System and method for manufacturing arthroplasty jigs

ABSTRACT

Disclosed herein is a method of computer generating a three-dimensional surface model of an arthroplasty target region of a bone forming a joint. The method may include: generating two-dimensional images of at least a portion of the bone; generating an open-loop contour line along the arthroplasty target region in at least some of the two-dimensional images; and generating the three-dimensional model of the arthroplasty target region from the open-loop contour lines.

FIELD OF THE INVENTION

The present invention relates to systems and methods for manufacturingcustomized arthroplasty cutting jigs. More specifically, the presentinvention relates to automated systems and methods manufacturing suchjigs.

BACKGROUND OF THE INVENTION

Over time and through repeated use, bones and joints can become damagedor worn. For example, repetitive strain on bones and joints (e.g.,through athletic activity), traumatic events, and certain diseases(e.g., arthritis) can cause cartilage in joint areas, which normallyprovides a cushioning effect, to wear down. When the cartilage wearsdown, fluid can accumulate in the joint areas, resulting in pain,stiffness, and decreased mobility.

Arthroplasty procedures can be used to repair damaged joints. During atypical arthroplasty procedure, an arthritic or otherwise dysfunctionaljoint can be remodeled or realigned, or an implant can be implanted intothe damaged region. Arthroplasty procedures may take place in any of anumber of different regions of the body, such as a knee, a hip, ashoulder, or an elbow.

One type of arthroplasty procedure is a total knee arthroplasty (“TKA”),in which a damaged knee joint is replaced with prosthetic implants. Theknee joint may have been damaged by, for example, arthritis (e.g.,severe osteoarthritis or degenerative arthritis), trauma, or a raredestructive joint disease. During a TKA procedure, a damaged portion inthe distal region of the femur may be removed and replaced with a metalshell, and a damaged portion in the proximal region of the tibia may beremoved and replaced with a channeled piece of plastic having a metalstem. In some TKA procedures, a plastic button may also be added underthe surface of the patella, depending on the condition of the patella.

Implants that are implanted into a damaged region may provide supportand structure to the damaged region, and may help to restore the damagedregion, thereby enhancing its functionality. Prior to implantation of animplant in a damaged region, the damaged region may be prepared toreceive the implant. For example, in a knee arthroplasty procedure, oneor more of the bones in the knee area, such as the femur and/or thetibia, may be treated (e.g., cut, drilled, reamed, and/or resurfaced) toprovide one or more surfaces that can align with the implant and therebyaccommodate the implant.

Accuracy in implant alignment is an important factor to the success of aTKA procedure. A one- to two-millimeter translational misalignment, or aone- to two-degree rotational misalignment, may result in imbalancedligaments, and may thereby significantly affect the outcome of the TKAprocedure. For example, implant misalignment may result in intolerablepost-surgery pain, and also may prevent the patient from having full legextension and stable leg flexion.

To achieve accurate implant alignment, prior to treating (e.g., cutting,drilling, reaming, and/or resurfacing) any regions of a bone, it isimportant to correctly determine the location at which the treatmentwill take place and how the treatment will be oriented. In some methods,an arthroplasty jig may be used to accurately position and orient afinishing instrument, such as a cutting, drilling, reaming, orresurfacing instrument on the regions of the bone. The arthroplasty jigmay, for example, include one or more apertures and/or slots that areconfigured to accept such an instrument.

A system and method has been developed for producing customizedarthroplasty jigs configured to allow a surgeon to accurately andquickly perform an arthroplasty procedure that restores thepre-deterioration alignment of the joint, thereby improving the successrate of such procedures. Specifically, the customized arthroplasty jigsare indexed such that they matingly receive the regions of the bone tobe subjected to a treatment (e.g., cutting, drilling, reaming, and/orresurfacing). The customized arthroplasty jigs are also indexed toprovide the proper location and orientation of the treatment relative tothe regions of the bone. The indexing aspect of the customizedarthroplasty jigs allows the treatment of the bone regions to be donequickly and with a high degree of accuracy that will allow the implantsto restore the patient's joint to a generally pre-deteriorated state.However, the system and method for generating the customized jigs oftenrelies on a human to “eyeball” bone models on a computer screen todetermine configurations needed for the generation of the customizedjigs. This is “eyeballing” or manual manipulation of the bone modes onthe computer screen is inefficient and unnecessarily raises the time,manpower and costs associated with producing the customized arthroplastyjigs. Furthermore, a less manual approach may improve the accuracy ofthe resulting jigs.

There is a need in the art for a system and method for reducing thelabor associated with generating customized arthroplasty jigs. There isalso a need in the art for a system and method for increasing theaccuracy of customized arthroplasty jigs.

SUMMARY

Disclosed herein is a method of manufacturing an arthroplasty jig. Inone embodiment, the method includes: generating two-dimensional imagesof at least a portion of a bone forming a joint; generating a firstthree-dimensional computer model of the at least a portion of the bonefrom the two-dimensional images; generating a second three-dimensionalcomputer model of the at least a portion of the bone from thetwo-dimensional images; causing the first and second three-dimensionalcomputer models to have in common a reference position, wherein thereference position includes at least one of a location and anorientation relative to an origin; generating a first type of data withthe first three-dimensional computer model; generating a second type ofdata with the second three-dimensional computer model; employing thereference position to integrate the first and second types of data intoan integrated jig data; using the integrated jig data at a manufacturingdevice to manufacture the arthroplasty jig.

Disclosed herein is a method of manufacturing an arthroplasty jig. Inone embodiment, the method includes: generating two-dimensional imagesof at least a portion of a bone forming a joint; extending an open-loopcontour line along an arthroplasty target region in at least some of thetwo-dimensional images; generating a three-dimensional computer model ofthe arthroplasty target region from the open-loop contour lines;generating from the three-dimensional computer model surface contourdata pertaining to the arthroplasty target area; and using the surfacecontour data at a manufacturing machine to manufacture the arthroplastyjig.

Disclosed herein is a method of manufacturing an arthroplasty jig. Inone embodiment, the method includes: determining from an image at leastone dimension associated with a portion of a bone; comparing the atleast one dimension to dimensions of at least two candidate jig blanksizes; selecting the smallest of the jig blank sizes that issufficiently large to accommodate the at least one dimension; providinga jig blank of the selected size to a manufacturing machine; andmanufacturing the arthroplasty jig from the jig blank.

Disclosed herein are arthroplasty jigs manufactured according to any ofthe aforementioned methods of manufacture. In some embodiments, thearthroplasty jigs may be indexed to matingly receive arthroplasty targetregions of a joint bone. The arthroplasty jigs may also be indexed toorient saw cut slots and drill hole guides such that when thearthroplasty target regions are matingly received by the arthroplastyjig, the saw cuts and drill holes administered to the arthroplastytarget region via the saw cut slots and drill hole guides willfacilitate arthroplasty implants generally restoring the joint to apredegenerated state.

Disclosed herein is a method of computer generating a three-dimensionalsurface model of an arthroplasty target region of a bone forming ajoint. In one embodiment, the method includes: generatingtwo-dimensional images of at least a portion of the bone; generating anopen-loop contour line along the arthroplasty target region in at leastsome of the two-dimensional images; and generating the three-dimensionalmodel of the arthroplasty target region from the open-loop contourlines.

Disclosed herein is a method of generating a three-dimensionalarthroplasty jig computer model. In one embodiment, the method includes:comparing a dimension of at least a portion of a bone of a joint tocandidate jig blank sizes; and selecting from the candidate jig blanksizes a smallest jig blank size able to accommodate the dimensions ofthe at least a portion of the bone.

Disclosed herein is a method of generating a three-dimensionalarthroplasty jig computer model. In one embodiment, the method includes:forming an interior three-dimensional surface model representing anarthroplasty target region of at least a portion of a bone; forming anexterior three-dimensional surface model representing an exteriorsurface of a jig blank; and combining the interior surface model andexterior surface model to respectively form the interior surface andexterior surface of the three-dimensional arthroplasty jig computermodel.

Disclosed herein is a method of generating a production file associatedwith the manufacture of arthroplasty jigs. The method includes:generating first data associated a surface contour of an arthroplastytarget region of a joint bone; generating second data associated with atleast one of a saw cut and a drill hole to be administered to thearthroplasty target region during an arthroplasty procedure; andintegrating first and second data, wherein a positional relationship offirst data relative to an origin and a positional relationship of seconddata relative to the origin are coordinated with each other to begenerally identical during the respective generations of first andsecond data.

While multiple embodiments are disclosed, still other embodiments of thepresent invention will become apparent to those skilled in the art fromthe following detailed description, which shows and describesillustrative embodiments of the invention. As will be realized, theinvention is capable of modifications in various aspects, all withoutdeparting from the spirit and scope of the present invention.Accordingly, the drawings and detailed description are to be regarded asillustrative in nature and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram of a system for employing the automatedjig production method disclosed herein.

FIGS. 1B-1E are flow chart diagrams outlining the jig production methoddisclosed herein.

FIGS. 1F and 1G are, respectively, bottom and top perspective views ofan example customized arthroplasty femur jig.

FIGS. 1H and 1I are, respectively, bottom and top perspective views ofan example customized arthroplasty tibia jig.

FIG. 2A is an anterior-posterior image slice of the damaged lower orknee joint end of the patient's femur, wherein the image slice includesan open-loop contour line segment corresponding to the targeted regionof the damaged lower end.

FIG. 2B is a plurality of image slices with their respective open-loopcontour line segments, the open-loop contour line segments beingaccumulated to generate the 3D model of the targeted region.

FIG. 2C is a 3D model of the targeted region of the damaged lower end asgenerated using the open-loop contour line segments depicted in FIG. 2B.

FIG. 2D is an anterior-posterior image slice of the damaged lower orknee joint end of the patient's femur, wherein the image slice includesa closed-loop contour line corresponding to the femur lower end,including the targeted region.

FIG. 2E is a plurality of image slices with their respective closed-loopcontour line segments, the closed-loop contour lines being accumulatedto generate the 3D model of the femur lower end, including the targetedregion.

FIG. 2F is a 3D model of the femur lower end, including the targetedregion, as generated using the closed-loop contour lines depicted inFIG. 2B.

FIG. 2G is a flow chart illustrating an overview of the method ofproducing a femur jig.

FIG. 3A is a top perspective view of a left femoral cutting jig blankhaving predetermined dimensions.

FIG. 3B is a bottom perspective view of the jig blank depicted in FIG.3A.

FIG. 3C is plan view of an exterior side or portion of the jig blankdepicted in FIG. 3A.

FIG. 4A is a plurality of available sizes of left femur jig blanks, eachdepicted in the same view as shown in FIG. 3C.

FIG. 4B is a plurality of available sizes of right femur jig blanks,each depicted in the same view as shown in FIG. 3C.

FIG. 5 is an axial view of the 3D surface model or arthritic model ofthe patient's left femur as viewed in a direction extending distal toproximal.

FIG. 6 depicts the selected model jig blank of FIG. 3C superimposed onthe model femur lower end of FIG. 5.

FIG. 7A is an example scatter plot for selecting from a plurality ofcandidate jig blanks sizes a jig blank size appropriate for the lowerend of the patient's femur.

FIG. 7B is a flow diagram illustrating an embodiment of a process ofselecting an appropriately sized jig blank.

FIG. 8A is an exterior perspective view of a femur jig blank exteriorsurface model.

FIG. 8B is an interior perspective view if the femur jig blank exteriorsurface model of FIG. 8A.

FIG. 9A is a perspective view of the extracted jig blank exteriorsurface model being combined with the extracted femur surface model.

FIG. 9B is a perspective view of the extracted jig blank exteriorsurface model combined with the extracted femur surface model.

FIG. 9C is a cross section of the combined jig blank exterior surfacemodel and the femur surface model as taken along section line 9C-9C inFIG. 9B.

FIG. 10A is an exterior perspective view of the resulting femur jigmodel.

FIG. 10B is an interior perspective view of the femur jig model of FIG.10A.

FIG. 11 illustrates a perspective view of the integrated jig modelmating with the “arthritic model”.

FIG. 12A is an anterior-posterior image slice of the damaged upper orknee joint end of the patient's tibia, wherein the image slice includesan open-loop contour line segment corresponding to the target area ofthe damaged upper end.

FIG. 12B is a plurality of image slices with their respective open-loopcontour line segments, the open-loop contour line segments beingaccumulated to generate the 3D model of the target area.

FIG. 12C is a 3D model of the target area of the damaged upper end asgenerated using the open-loop contour line segments depicted in FIG.12B.

FIG. 13A is a top perspective view of a right tibia cutting jig blankhaving predetermined dimensions.

FIG. 13B is a bottom perspective view of the jig blank depicted in FIG.13A.

FIG. 13C is plan view of an exterior side or portion of the jig blank50BR depicted in FIG. 13A.

FIG. 14 is a plurality of available sizes of right tibia jig blanks,each depicted in the same view as shown in FIG. 13C.

FIG. 15 is an axial view of the 3D surface model or arthritic model ofthe patient's right tibia as viewed in a direction extending proximal todistal.

FIG. 16 depicts the selected model jig blank of FIG. 13C superimposed onthe model tibia upper end of FIG. 15.

FIG. 17A is an example scatter plot for selecting from a plurality ofcandidate jig blanks sizes a jig blank size appropriate for the upperend of the patient's tibia.

FIG. 17B is a flow diagram illustrating an embodiment of a process ofselecting an appropriately sized jig blank.

FIG. 18A is an exterior perspective view of a tibia jig blank exteriorsurface model.

FIG. 18B is an interior perspective view if the tibia jig blank exteriorsurface model of FIG. 18A.

FIG. 19A is a perspective view of the extracted jig blank exteriorsurface model being combined with the extracted tibia surface model.

FIGS. 19B-19D are perspective views of the extracted jig blank exteriorsurface model combined with the extracted tibia surface model.

FIG. 20A is an exterior perspective view of the resulting tibia jigmodel.

FIG. 20B is an interior perspective view of the tibia jig model of FIG.20A.

FIG. 21 illustrates a perspective view of the integrated jig modelmating with the “arthritic model”.

DETAILED DESCRIPTION

Disclosed herein are customized arthroplasty jigs 2 and systems 4 for,and methods of, producing such jigs 2. The jigs 2 are customized to fitspecific bone surfaces of specific patients. Depending on the embodimentand to a greater or lesser extent, the jigs 2 are automatically plannedand generated and may be similar to those disclosed in these three U.S.patent applications: U.S. patent application Ser. No. 11/656,323 to Parket al., titled “Arthroplasty Devices and Related Methods” and filed Jan.19, 2007; U.S. patent application Ser. No. 10/146,862 to Park et al.,titled “Improved Total Joint Arthroplasty System” and filed May 15,2002; and U.S. patent Ser. No. 11/642,385 to Park et al., titled“Arthroplasty Devices and Related Methods” and filed Dec. 19, 2006. Thedisclosures of these three U.S. patent applications are incorporated byreference in their entireties into this Detailed Description.

a. Overview of System and Method for Manufacturing CustomizedArthroplasty Cutting Jigs

For an overview discussion of the systems 4 for, and methods of,producing the customized arthroplasty jigs 2, reference is made to FIGS.1A-1E. FIG. 1A is a schematic diagram of a system 4 for employing theautomated jig production method disclosed herein. FIGS. 1B-1E are flowchart diagrams outlining the jig production method disclosed herein. Thefollowing overview discussion can be broken down into three sections.

The first section, which is discussed with respect to FIG. 1A and[blocks 100-125] of FIGS. 1B-1E, pertains to an example method ofdetermining, in a three-dimensional (“3D”) computer model environment,saw cut and drill hole locations 30, 32 relative to 3D computer modelsthat are termed restored bone models 28. The resulting “saw cut anddrill hole data” 44 is referenced to the restored bone models 28 toprovide saw cuts and drill holes that will allow arthroplasty implantsto restore the patient's joint to its pre-degenerated state.

The second section, which is discussed with respect to FIG. 1A and[blocks 100-105 and 130-145] of FIGS. 1B-1E, pertains to an examplemethod of importing into 3D computer generated jig models 38 3D computergenerated surface models 40 of arthroplasty target areas 42 of 3Dcomputer generated arthritic models 36 of the patient's joint bones. Theresulting “jig data” 46 is used to produce a jig customized to matinglyreceive the arthroplasty target areas of the respective bones of thepatient's joint.

The third section, which is discussed with respect to FIG. 1A and[blocks 150-165] of FIG. 1E, pertains to a method of combining orintegrating the “saw cut and drill hole data” 44 with the “jig data” 46to result in “integrated jig data” 48. The “integrated jig data” 48 isprovided to the CNC machine 10 for the production of customizedarthroplasty jigs 2 from jig blanks 50 provided to the CNC machine 10.The resulting customized arthroplasty jigs 2 include saw cut slots anddrill holes positioned in the jigs 2 such that when the jigs 2 matinglyreceive the arthroplasty target areas of the patient's bones, the cutslots and drill holes facilitate preparing the arthroplasty target areasin a manner that allows the arthroplasty joint implants to generallyrestore the patient's joint line to its pre-degenerated state.

As shown in FIG. 1A, the system 4 includes a computer 6 having a CPU 7,a monitor or screen 9 and an operator interface controls 11. Thecomputer 6 is linked to a medical imaging system 8, such as a CT or MRImachine 8, and a computer controlled machining system 10, such as a CNCmilling machine 10.

As indicated in FIG. 1A, a patient 12 has a joint 14 (e.g., a knee,elbow, ankle, wrist, hip, shoulder, skull/vertebrae orvertebrae/vertebrae interface, etc.) to be replaced. The patient 12 hasthe joint 14 scanned in the imaging machine 8. The imaging machine 8makes a plurality of scans of the joint 14, wherein each scan pertainsto a thin slice of the joint 14.

As can be understood from FIG. 1B, the plurality of scans is used togenerate a plurality of two-dimensional (“2D”) images 16 of the joint 14[block 100]. Where, for example, the joint 14 is a knee 14, the 2Dimages will be of the femur 18 and tibia 20. The imaging may beperformed via CT or MRI. In one embodiment employing MRI, the imagingprocess may be as disclosed in U.S. patent application Ser. No.11/946,002 to Park, which is entitled “Generating MRI Images Usable ForThe Creation Of 3D Bone Models Employed To Make Customized ArthroplastyJigs,” was filed Nov. 27, 2007 and is incorporated by reference in itsentirety into this Detailed Description.

As can be understood from FIG. 1A, the 2D images are sent to thecomputer 6 for creating computer generated 3D models. As indicated inFIG. 1B, in one embodiment, point P is identified in the 2D images 16[block 105]. In one embodiment, as indicated in [block 105] of FIG. 1A,point P may be at the approximate medial-lateral and anterior-posteriorcenter of the patient's joint 14. In other embodiments, point P may beat any other location in the 2D images 16, including anywhere on, nearor away from the bones 18, 20 or the joint 14 formed by the bones 18,20.

As described later in this overview, point P may be used to locate thecomputer generated 3D models 22, 28, 36 created from the 2D images 16and to integrate information generated via the 3D models. Depending onthe embodiment, point P, which serves as a position and/or orientationreference, may be a single point, two points, three points, a point plusa plane, a vector, etc., so long as the reference P can be used toposition and/or orient the 3D models 22, 28, 36 generated via the 2Dimages 16.

As shown in FIG. 1C, the 2D images 16 are employed to create computergenerated 3D bone-only (i.e., “bone models”) 22 of the bones 18, 20forming the patient's joint 14 [block 110]. The bone models 22 arelocated such that point P is at coordinates (X_(0-j), Y_(0-j), Z_(0-j))relative to an origin (X₀, Y₀, Z₀) of an X-Y-Z axis [block 110]. Thebone models 22 depict the bones 18, 20 in the present deterioratedcondition with their respective degenerated joint surfaces 24, 26, whichmay be a result of osteoarthritis, injury, a combination thereof, etc.

Computer programs for creating the 3D computer generated bone models 22from the 2D images 16 include: Analyze from AnalyzeDirect, Inc.,Overland Park, Kans.; Insight Toolkit, an open-source software availablefrom the National Library of Medicine Insight Segmentation andRegistration Toolkit (“ITK”), www.itk.org; 3D Slicer, an open-sourcesoftware available from www.slicer.org; Mimics from Materialise, AnnArbor, Mich.; and Paraview available at www.paraview.org.

As indicated in FIG. 1C, the 3D computer generated bone models 22 areutilized to create 3D computer generated “restored bone models” or“planning bone models” 28 wherein the degenerated surfaces 24, 26 aremodified or restored to approximately their respective conditions priorto degeneration [block 115]. Thus, the bones 18, 20 of the restored bonemodels 28 are reflected in approximately their condition prior todegeneration. The restored bone models 28 are located such that point Pis at coordinates (X_(0-j), Y_(0-j), Z_(0-j)) relative to the origin(X₀, Y₀, Z₀). Thus, the restored bone models 28 share the sameorientation and positioning relative to the origin (X₀, Y₀, Z₀) as thebone models 22.

In one embodiment, the restored bone models 28 are manually created fromthe bone models 22 by a person sitting in front of a computer 6 andvisually observing the bone models 22 and their degenerated surfaces 24,26 as 3D computer models on a computer screen 9. The person visuallyobserves the degenerated surfaces 24, 26 to determine how and to whatextent the degenerated surfaces 24, 26 surfaces on the 3D computer bonemodels 22 need to be modified to restore them to their pre-degeneratedcondition. By interacting with the computer controls 11, the person thenmanually manipulates the 3D degenerated surfaces 24, 26 via the 3Dmodeling computer program to restore the surfaces 24, 26 to a state theperson believes to represent the pre-degenerated condition. The resultof this manual restoration process is the computer generated 3D restoredbone models 28, wherein the surfaces 24′, 26′ are indicated in anon-degenerated state.

In one embodiment, the above-described bone restoration process isgenerally or completely automated. In other words, a computer programmay analyze the bone models 22 and their degenerated surfaces 24, 26 todetermine how and to what extent the degenerated surfaces 24, 26surfaces on the 3D computer bone models 22 need to be modified torestore them to their pre-degenerated condition. The computer programthen manipulates the 3D degenerated surfaces 24, 26 to restore thesurfaces 24, 26 to a state intended to represent the pre-degeneratedcondition. The result of this automated restoration process is thecomputer generated 3D restored bone models 28, wherein the surfaces 24′,26′ are indicated in a non-degenerated state.

As depicted in FIG. 1C, the restored bone models 28 are employed in apre-operative planning (“POP”) procedure to determine saw cut locations30 and drill hole locations 32 in the patient's bones that will allowthe arthroplasty joint implants to generally restore the patient's jointline to it pre-degenerative alignment [block 120].

In one embodiment, the POP procedure is a manual process, whereincomputer generated 3D implant models 34 (e.g., femur and tibia implantsin the context of the joint being a knee) and restored bone models 28are manually manipulated relative to each other by a person sitting infront of a computer 6 and visually observing the implant models 34 andrestored bone models 28 on the computer screen 9 and manipulating themodels 28, 34 via the computer controls 11. By superimposing the implantmodels 34 over the restored bone models 28, or vice versa, the jointsurfaces of the implant models 34 can be aligned or caused to correspondwith the joint surfaces of the restored bone models 28. By causing thejoint surfaces of the models 28, 34 to so align, the implant models 34are positioned relative to the restored bone models 28 such that the sawcut locations 30 and drill hole locations 32 can be determined relativeto the restored bone models 28.

In one embodiment, the POP process is generally or completely automated.For example, a computer program may manipulate computer generated 3Dimplant models 34 (e.g., femur and tibia implants in the context of thejoint being a knee) and restored bone models or planning bone models 28relative to each other to determine the saw cut and drill hole locations30, 32 relative to the restored bone models 28. The implant models 34may be superimposed over the restored bone models 28, or vice versa. Inone embodiment, the implant models 34 are located at point P′ (X_(0-k),Y_(0-k), Z_(0-k)) relative to the origin (X₀, Y₀, Z₀), and the restoredbone models 28 are located at point P (X_(0-j), Y_(0-j), Z_(0-j)). Tocause the joint surfaces of the models 28, 34 to correspond, thecomputer program may move the restored bone models 28 from point P(X_(0-j), Y_(0-j), Z_(0-j)) to point P′ (X_(0-k), Y_(0-k), Z_(0-k)), orvice versa. Once the joint surfaces of the models 28, 34 are in closeproximity, the joint surfaces of the implant models 34 may beshape-matched to align or correspond with the joint surfaces of therestored bone models 28. By causing the joint surfaces of the models 28,34 to so align, the implant models 34 are positioned relative to therestored bone models 28 such that the saw cut locations 30 and drillhole locations 32 can be determined relative to the restored bone models28.

As indicated in FIG. 1E, in one embodiment, the data 44 regarding thesaw cut and drill hole locations 30, 32 relative to point P′ (X_(0-k),Y_(0-k), Z_(0-k)) is packaged or consolidated as the “saw cut and drillhole data” 44 [block 145]. The “saw cut and drill hole data” 44 is thenused as discussed below with respect to [block 150] in FIG. 1E.

As can be understood from FIG. 1D, the 2D images 16 employed to generatethe bone models 22 discussed above with respect to [block 110] of FIG.1C are also used to create computer generated 3D bone and cartilagemodels (i.e., “arthritic models”) 36 of the bones 18, 20 forming thepatient's joint 14 [block 130]. Like the above-discussed bone models 22,the arthritic models 36 are located such that point P is at coordinates(X_(0-j), Y_(0-j), Z_(0-j)) relative to the origin (X₀, Y₀, Z₀) of theX-Y-Z axis [block 130]. Thus, the bone and arthritic models 22, 36 sharethe same location and orientation relative to the origin (X₀, Y₀, Z₀).This position/orientation relationship is generally maintainedthroughout the process discussed with respect to FIGS. 1B-1E.Accordingly, movements relative to the origin (X₀, Y₀, Z₀) of the bonemodels 22 and the various descendants thereof (i.e., the restored bonemodels 28, bone cut locations 30 and drill hole locations 32) are alsoapplied to the arthritic models 36 and the various descendants thereof(i.e., the jig models 38). Maintaining the position/orientationrelationship between the bone models 22 and arthritic models 36 andtheir respective descendants allows the “saw cut and drill hole data” 44to be integrated into the “jig data” 46 to form the “integrated jigdata” 48 employed by the CNC machine 10 to manufacture the customizedarthroplasty jigs 2.

Computer programs for creating the 3D computer generated arthriticmodels 36 from the 2D images 16 include: Analyze from AnalyzeDirect,Inc., Overland Park, Kans.; Insight Toolkit, an open-source softwareavailable from the National Library of Medicine Insight Segmentation andRegistration Toolkit (“ITK”), www.itk.org; 3D Slicer, an open-sourcesoftware available from www.slicer.org; Mimics from Materialise, AnnArbor, Mich.; and Paraview available at www.paraview.org.

Similar to the bone models 22, the arthritic models 36 depict the bones18, 20 in the present deteriorated condition with their respectivedegenerated joint surfaces 24, 26, which may be a result ofosteoarthritis, injury, a combination thereof, etc. However, unlike thebone models 22, the arthritic models 36 are not bone-only models, butinclude cartilage in addition to bone. Accordingly, the arthritic models36 depict the arthroplasty target areas 42 generally as they will existwhen the customized arthroplasty jigs 2 matingly receive thearthroplasty target areas 42 during the arthroplasty surgical procedure.

As indicated in FIG. 1D and already mentioned above, to coordinate thepositions/orientations of the bone and arthritic models 36, 36 and theirrespective descendants, any movement of the restored bone models 28 frompoint P to point P′ is tracked to cause a generally identicaldisplacement for the “arthritic models” 36 [block 135].

As depicted in FIG. 1D, computer generated 3D surface models 40 of thearthroplasty target areas 42 of the arthritic models 36 are importedinto computer generated 3D arthroplasty jig models 38 [block 140]. Thus,the jig models 38 are configured or indexed to matingly receive thearthroplasty target areas 42 of the arthritic models 36. Jigs 2manufactured to match such jig models 38 will then matingly receive thearthroplasty target areas of the actual joint bones during thearthroplasty surgical procedure.

In one embodiment, the procedure for indexing the jig models 38 to thearthroplasty target areas 42 is a manual process. The 3D computergenerated models 36, 38 are manually manipulated relative to each otherby a person sitting in front of a computer 6 and visually observing thejig models 38 and arthritic models 36 on the computer screen 9 andmanipulating the models 36, 38 by interacting with the computer controls11. In one embodiment, by superimposing the jig models 38 (e.g., femurand tibia arthroplasty jigs in the context of the joint being a knee)over the arthroplasty target areas 42 of the arthritic models 36, orvice versa, the surface models 40 of the arthroplasty target areas 42can be imported into the jig models 38, resulting in jig models 38indexed to matingly receive the arthroplasty target areas 42 of thearthritic models 36. Point P′ (X_(0-k), Y_(0-k), Z_(0-k)) can also beimported into the jig models 38, resulting in jig models 38 positionedand oriented relative to point P′ (X_(0-k), Y_(0-k), Z_(0-k)) to allowtheir integration with the bone cut and drill hole data 44 of [block125].

In one embodiment, the procedure for indexing the jig models 38 to thearthroplasty target areas 42 is generally or completely automated, asdiscussed in detail later in this Detailed Description. For example, acomputer program may create 3D computer generated surface models 40 ofthe arthroplasty target areas 42 of the arthritic models 36. Thecomputer program may then import the surface models 40 and point P′(X_(0-k), Y_(0-k), Z_(0-k)) into the jig models 38, resulting in the jigmodels 38 being indexed to matingly receive the arthroplasty targetareas 42 of the arthritic models 36. The resulting jig models 38 arealso positioned and oriented relative to point P′ (X_(0-k), Y_(0-k),Z_(0-k)) to allow their integration with the bone cut and drill holedata 44 of [block 125].

In one embodiment, the arthritic models 36 may be 3D volumetric modelsas generated from the closed-loop process discussed below with respectto FIGS. 2D-2F. In other embodiments, the arthritic models 36 may be 3Dsurface models as generated from the open-loop process discussed belowwith respect to FIGS. 2A-2C and 12A-12C.

As indicated in FIG. 1E, in one embodiment, the data regarding the jigmodels 38 and surface models 40 relative to point P′ (X_(0-k), Y_(0-k),Z_(0-k)) is packaged or consolidated as the “jig data” 46 [block 145].The “jig data” 46 is then used as discussed below with respect to [block150] in FIG. 1E.

As can be understood from FIG. 1E, the “saw cut and drill hole data” 44is integrated with the “jig data” 46 to result in the “integrated jigdata” 48 [block 150]. As explained above, since the “saw cut and drillhole data” 44, “jig data” 46 and their various ancestors (e.g., models22, 28, 36, 38) are matched to each other for position and orientationrelative to point P and P′, the “saw cut and drill hole data” 44 isproperly positioned and oriented relative to the “jig data” 46 forproper integration into the “jig data” 46. The resulting “integrated jigdata” 48, when provided to the CNC machine 10, results in jigs 2: (1)configured to matingly receive the arthroplasty target areas of thepatient's bones; and (2) having cut slots and drill holes thatfacilitate preparing the arthroplasty target areas in a manner thatallows the arthroplasty joint implants to generally restore thepatient's joint line to its pre-degenerated state.

As can be understood from FIGS. 1A and 1E, the “integrated jig data” 44is transferred from the computer 6 to the CNC machine 10 [block 155].Jig blanks 50 are provided to the CNC machine 10 [block 160], and theCNC machine 10 employs the “integrated jig data” to machine thearthroplasty jigs 2 from the jig blanks 50.

For a discussion of example customized arthroplasty cutting jigs 2capable of being manufactured via the above-discussed process, referenceis made to FIGS. 1F-1I. While, as pointed out above, the above-discussedprocess may be employed to manufacture jigs 2 configured forarthroplasty procedures involving knees, elbows, ankles, wrists, hips,shoulders, vertebra interfaces, etc., the jig examples depicted in FIGS.1F-1I are for total knee replacement (“TKR”) procedures. Thus, FIGS. 1Fand 1G are, respectively, bottom and top perspective views of an examplecustomized arthroplasty femur jig 2A, and FIGS. 1H and 1I are,respectively, bottom and top perspective views of an example customizedarthroplasty tibia jig 2B.

As indicated in FIGS. 1F and 1G, a femur arthroplasty jig 2A may includean interior side or portion 100 and an exterior side or portion 102.When the femur cutting jig 2A is used in a TKR procedure, the interiorside or portion 100 faces and matingly receives the arthroplasty targetarea 42 of the femur lower end, and the exterior side or portion 102 ison the opposite side of the femur cutting jig 2A from the interiorportion 100.

The interior portion 100 of the femur jig 2A is configured to match thesurface features of the damaged lower end (i.e., the arthroplasty targetarea 42) of the patient's femur 18. Thus, when the target area 42 isreceived in the interior portion 100 of the femur jig 2A during the TKRsurgery, the surfaces of the target area 42 and the interior portion 100match.

The surface of the interior portion 100 of the femur cutting jig 2A ismachined or otherwise formed into a selected femur jig blank 50A and isbased or defined off of a 3D surface model 40 of a target area 42 of thedamaged lower end or target area 42 of the patient's femur 18.

As indicated in FIGS. 1H and 1I, a tibia arthroplasty jig 2B may includean interior side or portion 104 and an exterior side or portion 106.When the tibia cutting jig 2B is used in a TKR procedure, the interiorside or portion 104 faces and matingly receives the arthroplasty targetarea 42 of the tibia upper end, and the exterior side or portion 106 ison the opposite side of the tibia cutting jig 2B from the interiorportion 104.

The interior portion 104 of the tibia jig 2B is configured to match thesurface features of the damaged upper end (i.e., the arthroplasty targetarea 42) of the patient's tibia 20. Thus, when the target area 42 isreceived in the interior portion 104 of the tibia jig 2B during the TKRsurgery, the surfaces of the target area 42 and the interior portion 104match.

The surface of the interior portion 104 of the tibia cutting jig 2B ismachined or otherwise formed into a selected tibia jig blank 50B and isbased or defined off of a 3D surface model 40 of a target area 42 of thedamaged upper end or target area 42 of the patient's tibia 20.

b. Overview of Automated Process for Indexing 3D Arthroplasty Jig Modelsto Arthroplasty Target Areas

As mentioned above with respect to [block 140] of FIG. 1D, the processfor indexing the 3D arthroplasty jig models 38 to the arthroplastytarget areas 42 can be automated. A discussion of an example of such anautomated process will now concern the remainder of this DetailedDescription, beginning with an overview of the automated indexingprocess.

As can be understood from FIG. 1A and [blocks 100-105] of FIG. 1B, apatient 12 has a joint 14 (e.g., a knee, elbow, ankle, wrist, shoulder,hip, vertebra interface, etc.) to be replaced. The patient 12 has thejoint 14 scanned in an imaging machine 10 (e.g., a CT, MRI, etc.machine) to create a plurality of 2D scan images 16 of the bones (e.g.,femur 18 and tibia 20) forming the patient's joint 14 (e.g., knee). Eachscan image 16 is a thin slice image of the targeted bone(s) 18, 20. Thescan images 16 are sent to the CPU 7, which employs an open-loop imageanalysis along targeted features 42 of the scan images 16 of the bones18, 20 to generate a contour line for each scan image 16 along theprofile of the targeted features 42.

As can be understood from FIG. 1A and [block 110] of FIG. 1C, the CPU 7compiles the scan images 16 and, more specifically, the contour lines togenerate 3D computer surface models (“arthritic models”) 36 of thetargeted features 42 of the patient's joint bones 18, 20. In the contextof total knee replacement (“TKR”) surgery, the targeted features 42 maybe the lower or knee joint end of the patient's femur 18 and the upperor knee joint end of the patient's tibia 20. More specifically, thetargeted features 42 may be the tibia contacting articulating surface ofthe patient's femur 18 and the femur contacting articulating surface ofthe patient's tibia 20.

In some embodiments, the “arthritic models” 36 may be surface models orvolumetric solid models respectively formed via an open-loop orclosed-loop process such that the contour lines are respectively open orclosed loops. In one embodiment discussed in detail herein, the“arthritic models” 36 may be surface models formed via an open-loopprocess. By employing an open-loop and surface model approach, asopposed to a closed-loop and volumetric solid model approach, thecomputer modeling process requires less processing capability and timefrom the CPU 7 and, as a result, is more cost effective.

The system 4 measures the anterior-posterior extent and medial-lateralextent of the target areas 42 of the “arthritic models” 36. Theanterior-posterior extent and medial-lateral extent may be used todetermine an aspect ratio, size and/or configuration for the 3D“arthritic models” 36 of the respective bones 18, 20. In one embodimentof a jig blank grouping and selection method discussed below, the aspectratio, size and/or configuration of the 3D “arthritic models” 36 of therespective bones 18, 20 may be used for comparison to the aspect ratio,size and/or configuration of 3D computer models of candidate jig blanks50 in a jig blank grouping and selection method discussed below. In oneembodiment of a jig blank grouping and selection method discussed below,the anterior-posterior and medial-lateral dimensions of the 3D“arthritic models” 36 of the respective bones 18, 20 may be used forcomparison to the anterior-posterior and medial-lateral dimensions of 3Dcomputer models of candidate jig blanks 50.

In the context of TKR, the jigs 2 will be femur and tibia arthroplastycutting jigs 2A, 2B, which are machined or otherwise formed from femurand tibia jig blanks 50A, 50B. A plurality of candidate jig blank sizesexists, for example, in a jig blank library. While each candidate jigblank may have a unique combination of anterior-posterior andmedial-lateral dimension sizes, in some embodiments, two or more of thecandidate jig blanks may share a common aspect ratio or configuration.The candidate jig blanks of the library may be grouped along slopedlines of a plot according to their aspect ratios. The system 4 employsthe jig blank grouping and selection method to select a jig blank 50from a plurality of available jig blank sizes contained in the jig blanklibrary. For example, the configurations, sizes and/or aspect ratios ofthe tibia and femur 3D arthritic models 36 are compared to theconfigurations, sizes and/or aspect ratios of the 3D models of thecandidate jig blanks with or without a dimensional comparison betweenthe arthritic models 36 and the models of the candidate jig blanks.

Alternatively, in one embodiment, the anterior-posterior andmedial-lateral dimensions of the target areas of the arthritic models 36of the patient's femur and tibia 18, 20 are increased via a mathematicalformula. The resulting mathematically modified anterior-posterior andmedial-lateral dimensions are then compared to the anterior-posteriorand medial-lateral dimensions of the models of the candidate jig blanks50A, 50B. In one embodiment, the jig blanks 50A, 50B selected are thejig blanks having anterior-posterior and medial-lateral dimensions thatare the closest in size to the mathematically modifiedanterior-posterior and medial-lateral dimensions of the patient's bones18, 20 without being exceeded by the mathematically modified dimensionsof the patient's bones 18, 20. In one embodiment, the jig blankselection method results in the selection of a jig blank 50 that is asnear as possible in size to the patient's knee features, therebyminimizing the machining involved in creating a jig 2 from a jig blank.

In one embodiment, as discussed with respect to FIGS. 1F-1I, eacharthroplasty cutting jig 2 includes an interior portion and an exteriorportion. The interior portion is dimensioned specific to the surfacefeatures of the patient's bone that are the focus of the arthroplasty.Thus, where the arthroplasty is for TKR surgery, the jigs will be afemur jig and/or a tibia jig. The femur jig will have an interiorportion custom configured to match the damaged surface of the lower orjoint end of the patient's femur. The tibia jig will have an interiorportion custom configured to match the damaged surface of the upper orjoint end of the patient's tibia.

In one embodiment, because of the jig blank grouping and selectionmethod, the exterior portion of each arthroplasty cutting jig 2 issubstantially similar in size to the patient's femur and tibia 3Darthritic models 36. However, to provide adequate structural integrityfor the cuffing jigs 2, the exterior portions of the jigs 2 may bemathematically modified to cause the exterior portions of the jigs 2 toexceed the 3D femur and tibia models in various directions, therebyproviding the resulting cutting jigs 2 with sufficient jig materialbetween the exterior and interior portions of the jigs 2 to provideadequate structural strength.

As can be understood from [block 140] of FIG. 1D, once the system 4selects femur and tibia jig blanks 50 of sizes and configurationssufficiently similar to the sizes and configurations of the patient'sfemur and tibia computer arthritic models 36, the system 4 superimposesthe 3D computer surface models 40 of the targeted features 42 of thefemur 18 and tibia 20 onto the interior portion of the respective 3Dcomputer models of the selected femur and tibia jigs 38, or moreappropriately in one version of the present embodiment, the jig blanks50. The result, as can be understood from [block 145] of FIG. 1E, iscomputer models of the femur and tibia jigs 2 in the form of “jig data”46, wherein the femur and tibia jig computer models have: (1) respectiveexterior portions closely approximating the overall size andconfiguration of the patient's femur and tibia; and (2) respectiveinterior portions having surfaces that match the targeted features 42 ofthe patient's femur 18 and tibia 20.

The system 4 employs the data from the jig computer models (i.e., “jigdata” 46) to cause the CNC machine 10 to machine the actual jigs 2 fromactual jig blanks. The result is the automated production of actualfemur and tibia jigs 2 having: (1) exterior portions generally matchingthe patient's actual femur and tibia with respect to size and overallconfiguration; and (2) interior portions having patient-specificdimensions and configurations corresponding to the actual dimensions andconfigurations of the targeted features 42 of the patient's femur andtibia. The systems 4 and methods disclosed herein allow for theefficient manufacture of arthroplasty jigs 2 customized for the specificbone features of a patient.

The jigs 2 and systems 4 and methods of producing such jigs areillustrated herein in the context of knees and TKR surgery. However,those skilled in the art will readily understand the jigs 2 and system 4and methods of producing such jigs can be readily adapted for use in thecontext of other joints and joint replacement surgeries, e.g., elbows,shoulders, hips, etc. Accordingly, the disclosure contained hereinregarding the jigs 2 and systems 4 and methods of producing such jigsshould not be considered as being limited to knees and TKR surgery, butshould be considered as encompassing all types of joint surgeries.

c. Defining a 3D Surface Model of an Arthroplasty Target Area of a FemurLower End for Use as a Surface of an Interior Portion of a FemurArthroplasty Cutting Jig.

For a discussion of a method of generating a 3D model 40 of a targetarea 42 of a damaged lower end 204 of a patient's femur 18, reference ismade to FIGS. 2A-2G. FIG. 2A is an anterior-posterior (“AP”) image slice208 of the damaged lower or knee joint end 204 of the patient's femur18, wherein the image slice 208 includes an open-loop contour linesegment 210 corresponding to the target area 42 of the damaged lower end204. FIG. 2B is a plurality of image slices (16-1, 16-1, 16-2, . . .16-n) with their respective open-loop contour line segments (210-1,210-2, . . . 210-n), the open-loop contour line segments 210 beingaccumulated to generate the 3D model 40 of the target area 42. FIG. 2Cis a 3D model 40 of the target area 42 of the damaged lower end 204 asgenerated using the open-loop contour line segments (16-1, 16-2, . . .16-n) depicted in FIG. 2B. FIGS. 2D-2F are respectively similar to FIGS.2A-2C, except FIGS. 2D-2F pertain to a closed-loop contour line asopposed to an open-loop contour line. FIG. 2G is a flow chartillustrating an overview of the method of producing a femur jig 2A.

As can be understood from FIGS. 1A, 1B and 2A, the imager 8 is used togenerate a 2D image slice 16 of the damaged lower or knee joint end 204of the patient's femur 18. As depicted in FIG. 2A, the 2D image 16 maybe an AP view of the femur 18. Depending on whether the imager 8 is aMRI or CT imager, the image slice 16 will be a MRI or CT slice. Thedamaged lower end 204 includes the posterior condyle 212, an anteriorfemur shaft surface 214, and an area of interest or targeted area 42that extends from the posterior condyle 212 to the anterior femur shaftsurface 214. The targeted area 42 of the femur lower end may be thearticulating contact surfaces of the femur lower end that contactcorresponding articulating contact surfaces of the tibia upper or kneejoint end.

As shown in FIG. 2A, the image slice 16 may depict the cancellous bone216, the cortical bone 218 surrounding the cancellous bone, and thearticular cartilage lining portions of the cortical bone 218. Thecontour line 210 may extend along the targeted area 42 and immediatelyadjacent the cortical bone and cartilage to outline the contour of thetargeted area 42 of the femur lower end 204. The contour line 210extends along the targeted area 42 starting at point A on the posteriorcondyle 212 and ending at point B on the anterior femur shaft surface214.

In one embodiment, as indicated in FIG. 2A, the contour line 210 extendsalong the targeted area 42, but not along the rest of the surface of thefemur lower end 204. As a result, the contour line 210 forms anopen-loop that, as will be discussed with respect to FIGS. 2B and 2C,can be used to form an open-loop region or 3D computer model 40, whichis discussed with respect to [block 140] of FIG. 1D and closely matchesthe 3D surface of the targeted area 42 of the femur lower end. Thus, inone embodiment, the contour line is an open-loop and does not outlinethe entire cortical bone surface of the femur lower end 204. Also, inone embodiment, the open-loop process is used to form from the 3D images16 a 3D surface model 36 that generally takes the place of the arthriticmodel 36 discussed with respect to [blocks 125-140] of FIG. 1D and whichis used to create the surface model 40 used in the creation of the “jigdata” 46 discussed with respect to [blocks 145-150] of FIG. 1E.

In one embodiment and in contrast to the open-loop contour line 210depicted in FIGS. 2A and 2B, the contour line is a closed-loop contourline 210′ that outlines the entire cortical bone surface of the femurlower end and results in a closed-loop area, as depicted in FIG. 2D. Theclosed-loop contour lines 210′-2, . . . 210′-n of each image slice 16-1,. . . 16-n are combined, as indicated in FIG. 2E. A closed-loop area mayrequire the analysis of the entire surface region of the femur lower end204 and result in the formation of a 3D model of the entire femur lowerend 204 as illustrated in FIG. 2F. Thus, the 3D surface model resultingfrom the closed-loop process ends up having in common much, if not all,the surface of the 3D arthritic model 36. In one embodiment, theclosed-loop process may result in a 3D volumetric anatomical joint solidmodel from the 2D images 16 via applying mathematical algorithms. U.S.Pat. No. 5,682,886, which was filed Dec. 26, 1995 and is incorporated byreference in its entirety herein, applies a snake algorithm forming acontinuous boundary or closed-loop. After the femur has been outlined, amodeling process is used to create the 3D surface model, for example,through a Bezier patches method. Other 3D modeling processes, e.g.,commercially-available 3D construction software as listed in other partsof this Detailed Description, are applicable to 3D surface modelgeneration for closed-loop, volumetric solid modeling.

In one embodiment, the closed-loop process is used to form from the 3Dimages 16 a 3D volumetric solid model 36 that is essentially the same asthe arthritic model 36 discussed with respect to [blocks 125-140] ofFIG. 1D. The 3D volumetric solid model 36 is used to create the surfacemodel 40 used in the creation of the “jig data” 46 discussed withrespect to [blocks 145-150] of FIG. 1E.

The formation of a 3D volumetric solid model of the entire femur lowerend employs a process that may be much more memory and time intensivethan using an open-loop contour line to create a 3D model of thetargeted area 42 of the femur lower end. Accordingly, although theclosed-loop methodology may be utilized for the systems and methodsdisclosed herein, for at least some embodiments, the open-loopmethodology may be preferred over the closed-loop methodology.

An example of a closed-loop methodology is disclosed in U.S. patentapplication Ser. No. 11/641,569 to Park, which is entitled “ImprovedTotal Joint Arthroplasty System” and was filed Jan. 19, 2007. Thisapplication is incorporated by reference in its entirety into thisDetailed Description.

As can be understood from FIGS. 2B and 2G, the imager 8 generates aplurality of image slices (16-1, 16-2 . . . 16-n) via repetitive imagingoperations [block 1000]. Each image slice 16 has an open-loop contourline (210-1, 210-2 . . . 210-n) extending along the targeted region 42in a manner as discussed with respect to FIG. 2A [block 1005]. In oneembodiment, each image slice is a two-millimeter 2D image slice 16. Thesystem 100 compiles the plurality of 2D image slices (16-1, 16-2 . . .16-n) and, more specifically, the plurality of open-loop contour lines(210-1, 210-2, . . . 210-n) into the 3D femur surface computer model 40depicted in FIG. 2C [block 1010]. This process regarding the generationof the surface model 40 is also discussed in the overview section withrespect to [blocks 100-105] of FIG. 1B and [blocks 130-140] of FIG. 1D.A similar process may be employed with respect to the closed-loopcontour lines depicted in FIGS. 2D-2F.

As can be understood from FIG. 2C, the 3D femur surface computer model40 is a 3D computer representation of the targeted region 42 of thefemur lower end. In one embodiment, the 3D representation of thetargeted region 42 is a 3D representation of the articulated tibiacontact surfaces of the femur distal end. As the open-loop generated 3Dmodel 40 is a surface model of the relevant tibia contacting portions ofthe femur lower end, as opposed to a 3D model of the entire surface ofthe femur lower end as would be a result of a closed-loop contour line,the open-loop generated 3D model 40 is less time and memory intensive togenerate.

In one embodiment, the open-loop generated 3D model 40 is a surfacemodel of the tibia facing end face of the femur lower end, as opposed a3D model of the entire surface of the femur lower end. The 3D model 40can be used to identify the area of interest or targeted region 42,which, as previously stated, may be the relevant tibia contactingportions of the femur lower end. Again, the open-loop generated 3D model40 is less time and memory intensive to generate as compared to a 3Dmodel of the entire surface of the femur distal end, as would begenerated by a closed-loop contour line. Thus, for at least someversions of the embodiments disclosed herein, the open-loop contour linemethodology is preferred over the closed-loop contour line methodology.However, the system 4 and method disclosed herein may employ either theopen-loop or closed-loop methodology and should not be limited to one orthe other.

Regardless of whether the 3D model 40 is a surface model of the targetedregion 42 (i.e., a 3D surface model generated from an open-loop processand acting as the arthritic model 22) or the entire tibia facing endface of the femur lower end (i.e., a 3D volumetric solid model generatedfrom a closed-loop process and acting as the arthritic model 22), thedata pertaining to the contour lines 210 can be converted into the 3Dcontour computer model 40 via the surface rendering techniques disclosedin any of the aforementioned U.S. patent applications to Park. Forexample, surface rending techniques employed include point-to-pointmapping, surface normal vector mapping, local surface mapping, andglobal surface mapping techniques. Depending on the situation, one or acombination of mapping techniques can be employed.

In one embodiment, the generation of the 3D model 40 depicted in FIG. 2Cmay be formed by using the image slices 16 to determine locationcoordinate values of each of a sequence of spaced apart surface pointsin the open-loop region of FIG. 2B. A mathematical model may then beused to estimate or compute the 3D model 40 in FIG. 2C. Examples ofother medical imaging computer programs that may be used include, butare not limited to: Analyze from AnalyzeDirect, Inc. of Overland Park,Kans.; open-source software such as Paraview of Kitware, Inc.; InsightToolkit (“ITK”) available at www.itk.org; 3D Slicer available atwww.slicer.org; and Mimics from Materialise of Ann Arbor, Mich.

Alternatively or additionally to the aforementioned systems forgenerating the 3D model 40 depicted in FIG. 2C, other systems forgenerating the 3D model 40 of FIG. 2C include the surface renderingtechniques of the Non-Uniform Rational B-spline (“NURB”) program or theBézier program. Each of these programs may be employed to generate the3D contour model 40 from the plurality of contour lines 210.

In one embodiment, the NURB surface modeling technique is applied to theplurality of image slices 16 and, more specifically, the plurality ofopen-loop contour lines 210 of FIG. 2B. The NURB software generates a 3Dmodel 40 as depicted in FIG. 2C, wherein the 3D model 40 has areas ofinterest or targeted regions 42 that contain both a mesh and its controlpoints. For example, see Ervin et al., Landscape Modeling, McGraw-Hill,2001, which is hereby incorporated by reference in its entirety intothis Detailed Description.

In one embodiment, the NURB surface modeling technique employs thefollowing surface equation:

${{G\left( {s,t} \right)} = \frac{\sum\limits_{i = 0}^{k\; 1}\;{\sum\limits_{j = 0}^{k\; 2}\;{{W\left( {i,j} \right)}{P\left( {i,j} \right)}{b_{i}(s)}{b_{j}(t)}}}}{\sum\limits_{i = 0}^{k\; 1}\;{\sum\limits_{j = 0}^{k\; 2}\;{{W\left( {i,j} \right)}{b_{i}(s)}{b_{j}(t)}}}}},$wherein P(i,j) represents a matrix of vertices with nrows=(k1+1) andncols=(k2+1), W(i,j) represents a matrix of vertex weights of one pervertex point, b_(i)(s) represents a row-direction basis or blending ofpolynomial functions of degree M1, b_(j)(t) represents acolumn-direction basis or blending polynomial functions of degree M2, srepresents a parameter array of row-direction knots, and t represents aparameter array of column-direction knots.

In one embodiment, the Bézier surface modeling technique employs theBézier equation (1972, by Pierre Bézier) to generate a 3D model 40 asdepicted in FIG. 2C, wherein the model 40 has areas of interest ortargeted regions 42. A given Bézier surface of order (n, m) is definedby a set of (n+1)(m+1) control points k_(i,j). It maps the unit squareinto a smooth-continuous surface embedded within a space of the samedimensionality as (k_(i,j)). For example, if k are all points in afour-dimensional space, then the surface will be within afour-dimensional space. This relationship holds true for aone-dimensional space, a two-dimensional space, a fifty-dimensionalspace, etc.

A two-dimensional Bézier surface can be defined as a parametric surfacewhere the position of a point p as a function of the parametriccoordinates u, v is given by:

${p\left( {u,v} \right)} = {\sum\limits_{i = 0}^{n}\;{\sum\limits_{j = 0}^{m}\;{{B_{i}^{n}(u)}{B_{j}^{m}(v)}k_{i,j}}}}$evaluated over the unit square, where

${B_{i}^{n}(u)} = {\begin{pmatrix}n \\i\end{pmatrix}{u^{i}\left( {1 - u} \right)}^{n - i}}$is a Bernstein polynomial and

$\begin{pmatrix}n \\i\end{pmatrix} = \frac{n!}{{i!}*{\left( {n - i} \right)!}}$is the binomial coefficient. See Grune et al, On Numerical Algorithm andInteractive Visualization for Optimal Control Problems, Journal ofComputation and Visualization in Science, Vol. 1, No. 4, July 1999,which is hereby incorporated by reference in its entirety into thisDetailed Description.

Various other surface rendering techniques are disclosed in otherreferences. For example, see the surface rendering techniques disclosedin the following publications: Lorensen et al., Marching Cubes: A highResolution 3d Surface Construction Algorithm, Computer Graphics, 21-3:163-169, 1987; Farin et al., NURB Curves & Surfaces: From ProjectiveGeometry to Practical Use, Wellesley, 1995; Kumar et al, RobustIncremental Polygon Triangulation for Surface Rendering, WSCG, 2000;Fleischer et al., Accurate Polygon Scan Conversion Using Half-OpenIntervals, Graphics Gems III, p. 362-365, code: p. 599-605, 1992; Foleyet al., Computer Graphics: Principles and Practice, Addison Wesley,1990; Glassner, Principles of Digital Image Synthesis, Morgan Kaufmann,1995, all of which are hereby incorporated by reference in theirentireties into this Detailed Description.

d. Selecting a Jig Blank Most Similar in Size and/or Configuration tothe Size of the Patient's Femur Lower End.

As mentioned above, an arthroplasty jig 2, such as a femoral jig 2Aincludes an interior portion 100 and an exterior portion 102. Thefemoral jig 2A is formed from a femur jig blank 50A, which, in oneembodiment, is selected from a finite number of femur jig blank sizes.The selection of the femur jig blank 50A is based on a comparison of thedimensions of the patient's femur lower end 204 to the dimensions and/orconfigurations of the various sizes of femur jig blanks 50A to selectthe femur jig blank 50A most closely resembling the patient's femurlower end 204 with respect to size and/or configuration. This selectedfemur jig blank 50A has an outer or exterior side or surface 232 thatforms the exterior portion 232 of the femur jig 2A. The 3D surfacecomputer model 40 discussed with respect to the immediately precedingsection of this Detail Description is used to define a 3D surface 40into the interior side 230 of computer model of a femur jig blank 50A.

By selecting a femur jig blank 50A with an exterior portion 232 close insize to the patient's lower femur end 204, the potential for an accuratefit between the interior portion 230 and the patient's femur isincreased. Also, the amount of material that needs to be machined orotherwise removed from the jig blank 50A is reduced, thereby reducingmaterial waste and manufacturing time.

For a discussion of a method of selecting a jig blank 50 most closelycorresponding to the size and/or configuration of the patient's lowerfemur end, reference is first made to FIGS. 3-4B. FIG. 3A is a topperspective view of a left femoral cutting jig blank 50AL havingpredetermined dimensions. FIG. 3B is a bottom perspective view of thejig blank 50AL depicted in FIG. 3A. FIG. 3C is plan view of an exteriorside or portion 232 of the jig blank 50AL depicted in FIG. 3A. FIG. 4Ais a plurality of available sizes of left femur jig blanks 50AL, eachdepicted in the same view as shown in FIG. 3C. FIG. 4B is a plurality ofavailable sizes of right femur jig blanks 50AR, each depicted in thesame view as shown in FIG. 3C.

A common jig blank 50, such as the left jig blank 50AL depicted in FIGS.3A-3C and intended for creation of a left femur jig that can be usedwith a patient's left femur, may include a posterior edge 240, ananterior edge 242, a lateral edge 244, a medial edge 246, a lateralcondyle portion 248, a medial condyle portion 250, the exterior side 232and the interior side 230. The jig blank 50AL of FIGS. 3A-3C may be anyone of a number of left femur jig blanks 50AL available in a limitednumber of standard sizes. For example, the jig blank 50AL of FIGS. 3A-3Cmay be an i-th left femur jig blank, where i=1, 2, 3, 4, . . . m and mrepresents the maximum number of left femur jig blank sizes.

As indicated in FIG. 3C, the anterior-posterior extent JAi of the jigblank 50AL is measured from the anterior edge 242 to the posterior edge240 of the jig blank 50AL. The medial-lateral extent JMi of the jigblank 50AL is measured from the lateral edge 244 to the medial edge 246of the jig blank 50AL.

As can be understood from FIG. 4A, a limited number of left femur jigblank sizes may be available for selection as the left femur jig blanksize to be machined into the left femur cutting jig 2A. For example, inone embodiment, there are nine sizes (m=9) of left femur jig blanks 50ALavailable. As can be understood from FIG. 3C, each femur jig blank 50ALhas an anterior-posterior/medial-lateral aspect ratio defined as JAi toJMi (e.g., “JAi/JMi” aspect ratio). Thus, as can be understood from FIG.4A, jig blank 50AL-1 has an aspect ratio defined as “JA₁/JM₁”, jig blank50AL-2 has an aspect ratio defined as “JA₂/JM₂”, jig blank 50AL-3 has anaspect ratio defined as “JA₃/JM₃”, jig blank 50AL-4 has an aspect ratiodefined as “JA₄/JM₄”, jig blank 50AL-5 has an aspect ratio defined as“JA₅/JM₅”, jig blank 50AL-6 has an aspect ratio defined as “JA₆/JM₆”,jig blank 50AL-7 has an aspect ratio defined as “JA₇/JM₇”, jig blank50AL-8 has an aspect ratio defined as “JA₈/JM₈”, and jig blank 50AL-9has an aspect ratio defined as “JA₉/JM₉”.

The jig blank aspect ratio is utilized to design left femur jigs 2Adimensioned specific to the patient's left femur features. In oneembodiment, the jig blank aspect ratio can be the exterior dimensions ofthe left femur jig 2A. In another embodiment, the jig blank aspect ratiocan apply to the left femur jig fabrication procedure for selecting theleft jig blank 50AL having parameters close to the dimensions of thedesired left femur jig 2A. This embodiment can improve the costefficiency of the left femur jig fabrication process because it reducesthe amount of machining required to create the desired jig 2 from theselected jig blank 50.

In FIG. 4A, the N-1 direction represents increasing jig aspect ratiosmoving from jig 50AL-3 to jig 50AL-2 to jig 50AL-1, where“JA₃/JM₃”<“JA₂/JM₂”<“JA₁/JM₁”. The increasing ratios of the jigs 50ALrepresent the corresponding increment of JAi values, where the jigs' JMivalues remain the same. In other words, since JA₃<JA₂<JA₁, andJM₃=JM₂=JM₁, then “JA₃/JM₃”<“JA₂/JM₂”<“JA₁/JM₁”. One example of theincrement level can be an increase from 5% to 20%.

The same rationale applies to the N-2 direction and the N-3 direction.For example, the N-2 direction represents increasing jig aspect ratiosfrom jig 50AL-6 to jig 50AL-5 to jig 50AL-4, where“JA₄/JM₄”<“JA₅/JM₅”<“JA₆/JM₆”. The increasing ratios of the jigs 50ALrepresent the corresponding increment of JAi values, where the JMivalues remain the same. The N-3 direction represents increasing jigaspect ratios from jig 50AL-9 to jig 50AL-8 to jig 50AL-7, where“JA₇/JM₇”<“JA₈/JM₈”<“JA₉/JM₉”. The increasing ratios of the jigs 50ALrepresent the corresponding increment of JAi values, where the JMivalues remain the same.

As can be understood from the plot 300 depicted in FIG. 7 and discussedlater in this Detailed Discussion, the E-1 direction corresponds to thesloped line joining Group 1, Group 4 and Group 7. Similarly, the E-2direction corresponds to the sloped line joining Group 2, Group 5 andGroup 8. Also, the E-3 direction corresponds to the sloped line joiningGroup 3, Group 6 and Group 9.

As indicated in FIG. 4A, along direction E-2, the jig aspect ratiosremain the same among jigs 50AL-2, 50AL-5 and jig 50AL-8, where“JA₂/JM₂”=“JA₅/JM₅”=“JA₈/JM₈”. However, comparing to jig 50AL-2, jig50AL-5 is dimensioned larger and longer than jig 50AL-2. This is becausethe JA₅ value for jig 50AL-5 increases proportionally with the incrementof its JM₅ value in certain degrees in all X, Y, and Z-axis directions.In a similar fashion, jig 50AL-8 is dimensioned larger and longer thanjig 50AL-5 because the JA₈ increases proportionally with the incrementof its JM₈ value in certain degrees in all X, Y, and Z-axis directions.One example of the increment can be an increase from 5% to 20%.

The same rationale applies to directions E-1 and E-3. For example, inE-3 direction the jig ratios remain the same among the jigs 50AL-3,50AL-6 and jig 50AL-9. Compared to jig 50AL-3, jig 50AL-6 is dimensionedbigger and longer because both JM₆ and JA₆ values of jig 50AL-6 increaseproportionally in all X, Y, and Z-axis directions. Compared to jig50AL-6, jig 50AL-9 is dimensioned bigger and longer because both JM₉ andJA₉ values of jig 50AL-9 increase proportionally in all X, Y, andZ-axis.

As can be understood from FIG. 4B, a limited number of right femur jigblank sizes may be available for selection as the right femur jig blanksize to be machined into the right femur cutting jig 2A. For example, inone embodiment, there are nine sizes (m=9) of right femur jig blanks50AR available. As can be understood from FIG. 3, each femur jig blank50AR has an anterior-posterior/medial-lateral aspect ratio defined asJAi to JMi (e.g., “JAi/JMi” aspect ratio). Thus, as can be understoodfrom FIG. 4B, jig blank 50AR-1 has an aspect ratio defined as “JA₁/JM₁”,jig blank 50AR-2 has an aspect ratio defined as “JA₂/JM₂”, jig blank50AR-3 has an aspect ratio defined as “JA₃/JM₃”, jig blank 50AR-4 has anaspect ratio defined as “JA₄/JM₄”, jig blank 50AR-5 has an aspect ratiodefined as “JA₅/JM₅”, jig blank 50AR-6 has an aspect ratio defined as“JA₆/JM₆”, jig blank 50AR-7 has an aspect ratio defined as “JA₇/JM₇”,jig blank 50AR-8 has an aspect ratio defined as “JA₈/JM₈”, and jig blank50AR-9 has an aspect ratio defined as “JA₉/JM₉”.

The jig blank aspect ratio may be utilized to design right femur jigs 2Adimensioned specific to the patient's right femur features. In oneembodiment, the jig blank aspect ratio can be the exterior dimensions ofthe right femur jig 2A. In another embodiment, the jig blank aspectratio can apply to the right femur jig fabrication procedure forselecting the right jig blank 50AR having parameters close to thedimensions of the desired right femur jig 2A. This embodiment canimprove the cost efficiency of the right femur jig fabrication processbecause it reduces the amount of machining required to create thedesired jig 2 from the selected jig blank 50.

In FIG. 4B, the N-1 direction represents increasing jig aspect ratiosmoving from jig 50AR-3 to jig 50AR-2 to jig 50AR-1, where“JA₃/JM₃”<“JA₂/JM₂”<“JA₁/JM₁”. The increasing ratios of the jigs 50ARrepresent the corresponding increment of JAi values, where the jigs' JMivalues remain the same. In other words, since JA₃<JA₂<JA₁, andJM₃=JM₂=JM₁, then “JA₃/JM₃”<“JA₂/JM₂”<“JA₁/JM₁”. One example of theincrement level can be an increase from 5% to 20%.

The same rationale applies to the N-2 direction and the N-3 direction.For example, the N-2 direction represents increasing jig aspect ratiosfrom jig 50AR-6 to jig 50AR-5 to jig 50AR-4, where“JA₄/JM₄”<“JA₅/JM₅”<“JA₆/JM₆”. The increasing ratios of the jigs 50ARrepresent the corresponding increment of JAi values, where the JMivalues remain the same. The N-3 direction represents increasing jigaspect ratios from jig 50AR-9 to jig 50AR-8 to jig 50AR-7, where“JA₇/JM₇”<“JA₈/JM₈”<“JA₉/JM₉”. The increasing ratios of the jigs 50ARrepresent the corresponding increment of JAi values, where the JMivalues remain the same.

As indicated in FIG. 4B, along direction E-2, the jig aspect ratiosremain the same among jigs 50AR-2, 50AR-5 and jig 50AR-8, where“JA₂/JM₂”=“JA₅/JM₅”=“JA₈/JM₈”. However, comparing to jig 50AR-2, jig50AR-5 is dimensioned larger and longer than jig 50AR-2. This is becausethe JA₅ value for jig 50AR-5 increases proportionally with the incrementof its JM₅ value in certain degrees in all X, Y, and Z-axis directions.In a similar fashion, jig 50AR-8 is dimensioned larger and longer thanjig 50AR-5 because the JA₈ increases proportionally with the incrementof its JM₈ value in certain degrees in all X, Y, and Z-axis directions.One example of the increment can be an increase from 5% to 20%.

The same rationale applies to directions E-1 and E-3. For example, inE-3 direction the jig ratios remain the same among the jigs 50AR-3,50AR-6 and jig 50AR-9. Compared to jig 50AR-3, jig 50AR-6 is dimensionedbigger and longer because both JM₆ and JA₆ values of jig 50AR-6 increaseproportionally in all X, Y, and Z-axis directions. Compared to jig50AR-6, jig 50AR-9 is dimensioned bigger and longer because both JM₉ andJA₉ values of jig 50AR-9 increase proportionally in all X, Y, andZ-axis.

The dimensions of the lower or knee joint forming end 204 of thepatient's femur 18 can be determined by analyzing the 3D surface model40 or 3D arthritic model 36 in a manner similar to those discussed withrespect to the jig blanks 50. For example, as depicted in FIG. 5, whichis an axial view of the 3D surface model 40 or arthritic model 36 of thepatient's left femur 18 as viewed in a direction extending distal toproximal, the lower end 204 of the surface model 40 or arthritic model36 may include an anterior edge 262, a posterior edge 260, a medial edge264, a lateral edge 266, a medial condyle 268, and a lateral condyle270. The femur dimensions may be determined for the bottom end face ortibia articulating surface 204 of the patient's femur 18 via analyzingthe 3D surface model 40 of the 3D arthritic model 36. These femurdimensions can then be utilized to configure femur jig dimensions andselect an appropriate femur jig.

As shown in FIG. 5, the anterior-posterior extent fAP of the lower end204 of the patient's femur 18 (i.e., the lower end 204 of the surfacemodel 40 of the arthritic model 36, whether formed via open orclosed-loop analysis) is the length measured from the anterior edge 262of the femoral lateral groove to the posterior edge 260 of the femorallateral condyle 270. The medial-lateral extent fML of the lower end 204of the patient's femur 18 is the length measured from the medial edge264 of the medial condyle 268 to the lateral edge 266 of the lateralcondyle 270.

In one embodiment, the anterior-posterior extent fAP and medial-lateralextent fML of the femur lower end 204 can be used for an aspect ratiofAP/fML of the femur lower end. The aspect ratios fAP/fML of a largenumber (e.g., hundreds, thousands, tens of thousands, etc.) of patientknees can be compiled and statistically analyzed to determine the mostcommon aspect ratios for jig blanks that would accommodate the greatestnumber of patient knees. This information may then be used to determinewhich one, two, three, etc. aspect ratios would be most likely toaccommodate the greatest number of patient knees.

The system 4 analyzes the lower ends 204 of the patient's femur 18 asprovided via the surface model 40 of the arthritic model 36 (whether thearthritic model 36 is an 3D surface model generated via an open-loop ora 3D volumetric solid model generated via a closed-loop process) toobtain data regarding anterior-posterior extent fAP and medial-lateralextent fML of the femur lower ends 204. As can be understood from FIG.6, which depicts the selected model jig blank 50AL of FIG. 3Csuperimposed on the model femur lower end 204 of FIG. 5, the femurdimensional extents fAP, fML are compared to the jig blank dimensionalextents jAP, jML to determine which jig blank model to select as thestarting point for the machining process and the exterior surface modelfor the jig model.

As shown in FIG. 6, a prospective left femoral jig blank 50AL issuperimposed to mate with the left femur lower end 204 of the patient'sanatomical model as represented by the surface model 40 or arthriticmodel 36. The jig blank 50AL covers most of medial condyle 268 and thelateral condyle 270, leaving small exposed condyle regions including t1,t2, t3. The medial medial-lateral condyle region t1 represents theregion between the medial edge 264 of the medial condyle 268 and themedial edge 246 of the jig blank 50AL. The lateral medial-lateralcondyle region t2 represents the region between the lateral edge 266 ofthe lateral condyle 270 and the lateral edge 244 of the jig blank 50AL.The posterior anterior-posterior region t3 represents the condyle regionbetween the posterior edge 260 of the lateral condyle 270 and theposterior edge 240 of the jig blank 50AL.

The anterior edge 242 of the jig blank 50AL extends past the anterioredge 262 of the left femur lower end 204 as indicated by anterioranterior-posterior overhang t4. Specifically, the anterioranterior-posterior overhang t4 represents the region between theanterior edge 262 of the lateral groove of femur lower end 204 and theanterior edge 242 of the jig blank 50AL. By obtaining and employing thefemur anterior-posterior fAP data and the femur medial-lateral fML data,the system 4 can size the femoral jig blank 50AL according to thefollowing formulas: as jFML=fML−t1−t2 and jFAP=fAP−t3+t4, wherein jFMLis the medial-lateral extent of the femur jig blank 50AL and jFAP is theanterior-posterior extent of the femur jig blank 50AL. In oneembodiment, t1, t2, t3 and t4 will have the following ranges: 2 mm≦t1≦6mm; 2 mm≦t2≦6 mm; 2 mm≦t3≦12 mm; and 15 mm≦t4≦25 mm. In anotherembodiment, t1, t2, t3 and t4 will have the following values: t1=3 mm;t2=3 mm; t3=6 mm; and t4=20 mm.

FIG. 7A is an example scatter plot 300 for selecting from a plurality ofcandidate jig blanks sizes a jig blank size appropriate for the lowerend 204 of the patient's femur 18. In one embodiment, the X-axisrepresents the patient's femoral medial-lateral length fML inmillimeters, and the Y-axis represents the patient's femoralanterior-posterior length fAP in millimeters. In one embodiment, theplot is divided into a number of jig blank size groups, where each groupencompasses a region of the plot 300 and is associated with specificparameters JM_(r), JA_(r) of a specific candidate jig blank size.

In one embodiment, the example scatter plot 300 depicted in FIG. 7A hasnine jig blank size groups, each group pertaining to a single candidatejig blank size. However, depending on the embodiment, a scatter plot 300may have a greater or lesser number of jig blank size groups. The higherthe number of jig blank size groups, the higher the number of thecandidate jig blank sizes and the more dimension specific a selectedcandidate jig blank size will be to the patient's knee features and theresulting jig 2. The more dimension specific the selected candidate jigblank size, the lower the amount of machining required to produce thedesired jig 2 from the selected jig blank 50.

Conversely, the lower the number of jig blank size groups, the lower thenumber of candidate jig blank sizes and the less dimension specific aselected candidate jig blank size will be to the patient's knee featuresand the resulting jig 2. The less dimension specific the selectedcandidate jig blank size, the higher the amount of machining required toproduce the desired jig 2 from the selected jig blank 50, adding extraroughing during the jig fabrication procedure.

As can be understood from FIG. 7A, in one embodiment, the nine jig blanksize groups of the plot 300 have the parameters JM_(r), JA_(r) asfollows. Group 1 has parameters JM₁, JA₁. JM₁ represents themedial-lateral extent of the first femoral jig blank size, whereinJM₁=70 mm. JA₁ represents the anterior-posterior extent of the firstfemoral jig blank size, wherein JA₁=70.5 mm. Group 1 covers thepatient's femur fML and fAP data wherein 55 mm<fML<70 mm and 61mm<fAP<70.5 mm.

Group 2 has parameters JM₂, JA₂. JM₂ represents the medial-lateralextent of the second femoral jig blank size, wherein JM₂=70 mm. JA₂represents the anterior-posterior extent of the second femoral jig blanksize, wherein JA₂=61.5 mm. Group 2 covers the patient's femur fML andfAP data wherein 55 mm<fML<70 mm and 52 mm<fAP<61.5 mm.

Group 3 has parameters JM₃, JA₃. JM₃ represents the medial-lateralextent of the third femoral jig blank size, wherein JM₃=70 mm. JA₃represents the anterior-posterior extent of the third femoral jig blanksize, wherein JA₃=52 mm. Group 3 covers the patient's femur fML and fAPdata wherein 55 mm<fML<70 mm and 40 mm<fAP<52 mm.

Group 4 has parameters JM₄, JA₄. JM₄ represents the medial-lateralextent of the fourth femoral jig blank size, wherein JM₄=85 mm. JA₄represents the anterior-posterior extent of the fourth femoral jig blanksize, wherein JA₄=72.5 mm. Group 4 covers the patient's femur fML andfAP data wherein 70 mm<fML<85 mm and 63.5 mm<fAP<72.5 mm.

Group 5 has parameters JM₅, JA₅. JM₅ represents the medial-lateralextent of the fifth femoral jig blank size, wherein JM₅=85 mm. JA₅represents the anterior-posterior extent of the fifth femoral jig blanksize, wherein JA₅=63.5 mm. Group 5 covers the patient's femur fML andfAP data wherein 70 mm<fML<85 mm and 55 mm<fAP<63.5 mm.

Group 6 has parameters JM₆, JA₆. JM₆ represents the medial-lateralextent of the sixth femoral jig blank size, wherein JM₆=85 mm. JA₆represents the anterior-posterior extent of the sixth femoral jig blanksize, wherein JA₆=55 mm. Group 6 covers the patient's femur fML and fAPdata wherein 70 mm<fML<85 mm and 40 mm<fAP<55 mm.

Group 7 has parameters JM₇, JA₇. JM₇ represents the medial-lateralextent of the seventh femoral jig blank size, wherein JM₇=100 mm. JA₇represents the anterior-posterior extent of the seventh femoral jigblank size, wherein JA₇=75 mm. Group 7 covers the patient's femur fMLand fAP data wherein 85 mm<fML<100 mm and 65 mm<fAP<75 mm.

Group 8 has parameters JM₈, JA₈. JM₈ represents the medial-lateralextent of the eighth femoral jig blank size, wherein JM₈=100 mm. JA₈represents the anterior-posterior extent of the eighth femoral jig blanksize, wherein JA₈=65 mm. Group 8 covers the patient's femur fML and fAPdata wherein 85 mm<fML<100 mm and 57.5 mm<fAP<65 mm.

Group 9 has parameters JM₉, JA₉. JM₉ represents the medial-lateralextent of the ninth femoral jig blank size, wherein JM₉=100 mm. JA₉represents the anterior-posterior extent of the ninth femoral jig blanksize, wherein JA₉=57.5 mm. Group 9 covers the patient's femur fML andfAP data wherein 85 mm<fML<100 mm and 40 mm<fAP<57.5 mm.

As can be understood from FIG. 7B, which is a flow diagram illustratingan embodiment of a process of selecting an appropriately sized jigblank, bone anterior-posterior and medial-lateral extents fAP, fML aredetermined for the lower end 204 of the surface model 40 of thearthritic model 36 [block 2000]. The bone extents fAP, fML of the lowerend 204 are mathematically modified according to the above discussedjFML and jFAP formulas to arrive at the minimum femur jig blankanterior-posterior extent jFAP and medial-lateral extent jFML [block2010]. The mathematically modified bone extents fAP, fML or, morespecifically, the minimum femur jig blank anterior-posterior andmedial-lateral extents jFAP, jFML are referenced against the jig blankdimensions in the plot 300 of FIG. 7A [block 2020]. The plot 300 maygraphically represent the extents of candidate femur jig blanks forminga jig blank library. The femur jig blank 50A is selected to be the jigblank size having the smallest extents that are still sufficiently largeto accommodate the minimum femur jig blank anterior-posterior andmedial-lateral extents JFAP, jFML [block 2030].

In one embodiment, the exterior of the selected jig blank size is usedfor the exterior surface model of the jig model, as discussed below. Inone embodiment, the selected jig blank size corresponds to an actual jigblank that is placed in the CNC machine and milled down to the minimumfemur jig blank anterior-posterior and medial-lateral extents jFAP, jFMLto machine or otherwise form the exterior surface of the femur jig 2A.

The method outlined in FIG. 7B and in reference to the plot 300 of FIG.7A can be further understood from the following example. As measured inFIG. 6 with respect to the lower end 204 of the patient's femur 18, theextents of the patient's femur are as follows: fML=79.2 mm and fAP=54.5mm [block 2000]. As previously mentioned, the lower end 204 may be partof the surface model 40 of the arthritic model 36. Once the fML and fAPmeasurements are determined from the lower end 204, the correspondingjig jFML data and jig jFAP data can be determined via theabove-described jFML and jFAP formulas: jFML 32 fML−t1−t2, wherein t1=3mm and t2=3 mm; and jFAP=fAP−t3+t4, wherein t3=6 mm and t4=20 mm [block2010]. The result of the jFML and jFAP formulas is jFML=73.2 mm andjFAP=68.5 mm.

As can be understood from the plot 300 of FIG. 7, the determined jigdata (i.e., jFML=73.2 mm and jFAP=68.5 mm) falls in Group 4 of the plot300. Group 4 has the predetermined femur jig blank parameters (JM₄, JA₄)of JM₄=85 mm and JA₄=72.5 mm. These predetermined femur jig blankparameters are the smallest of the various groups that are stillsufficiently large to meet the minimum femur blank extents jFAP, jFML[block 2020]. These predetermined femur jig blank parameters (JM₄=85 mmand JA₄=72.5 mm) may be selected as the appropriate femur jig blank size[block 2030].

In one embodiment, the predetermined femur jig blank parameters (85 mm,72.5 mm) can apply to the femur exterior jig dimensions as shown in FIG.3C. In other words, the jig blank exterior is used for the jig modelexterior as discussed with respect to FIGS. 8A-9C. Thus, the exterior ofthe femur jig blank 50A undergoes no machining, and the unmodifiedexterior of the jig blank 50A with its predetermined jig blankparameters (85 mm, 72.5 mm) serves as the exterior of the finished femurjig 2A.

In another embodiment, the femur jig blank parameters (85 mm, 72.5 mm)can be selected for jig fabrication in the machining process. Thus, afemur jig blank 50A having predetermined parameters (85 mm, 72.5 mm) isprovided to the machining process such that the exterior of the femurjig blank 50A will be machined from its predetermined parameters (85 mm,72.5 mm) down to the desired femur jig parameters (73.2, 68.5 mm) tocreate the finished exterior of the femur jig 2A. As the predeterminedparameters (85 mm, 72.5 mm) are selected to be relatively close to thedesired femur jig parameters (73.2, 68.5 mm), machining time andmaterial waste are reduced.

While it may be advantageous to employ the above-described jig blankselection method to minimize material waste and machining time, in someembodiments, a jig blank will simply be provided that is sufficientlylarge to be applicable to all patient bone extents fAP, fML. Such a jigblank is then machined down to the desired jig blank extents jFAP, jFML,which serve as the exterior surface of the finished jig 2A.

In one embodiment, the number of candidate jig blank size groupsrepresented in the plot 300 is a function of the number of jig blanksizes offered by a jig blank manufacturer. For example, a first plot 300may pertain only to jig blanks manufactured by company A, which offersnine jig blank sizes. Accordingly, the plot 300 has nine jig blank sizegroups. A second plot 300 may pertain only to jig blanks manufactured bycompany B, which offers twelve jig blank size groups. Accordingly, thesecond plot 300 has twelve jig blank size groups.

A plurality of candidate jig blank sizes exist, for example, in a jigblank library as represented by the plot 300 of FIG. 7B. While eachcandidate jig blank may have a unique combination of anterior-posteriorand medial-lateral dimension sizes, in some embodiments, two or more ofthe candidate jig blanks may share a common aspect ratio jAP/jML orconfiguration. The candidate jig blanks of the library may be groupedalong sloped lines of the plot 300 according to their aspect ratiosjAP/jML.

In one embodiment, the jig blank aspect ratio jAP/jML may be used totake a workable jig blank configuration and size it up or down to fitlarger or smaller individuals.

As can be understood from FIG. 7A, a series of 98 OA patients havingknee disorders were entered into the plot 300 as part of a femur jigdesign study. Each patient's femur fAP and fML data was measured andmodified via the above-described jFML and jFAP formulas to arrive at thepatient's jig blank data (jFML, jFAP). The patient's jig blank data wasthen entered into the plot 300 as a point. As can be understood fromFIG. 7A, no patient point lies outside the parameters of an availablegroup. Such a process can be used to establish group parameters and thenumber of needed groups.

In one embodiment, the selected jig blank parameters can be the femoraljig exterior dimensions that are specific to patient's knee features. Inanother embodiment, the selected jig blank parameters can be chosenduring fabrication process.

e. Formation of 3D Femoral Jig Model.

For a discussion of an embodiment of a method of generating a 3D femurjig model 346 generally corresponding to the “integrated jig data” 48discussed with respect to [block 150] of FIG. 1E, reference is made toFIGS. 3A-3C, FIGS. 8A-8B, FIGS. 9A-9C and FIG. 10A-10B. FIGS. 3A-3C arevarious views of a femur jig blank 50A. FIGS. 8A-8B are, respectively,exterior and interior perspective views of a femur jig blank exteriorsurface model 232M. FIGS. 9A and 9B are exterior perspective views ofthe jig blank exterior model 232M and bone surface model 40 beingcombined, and FIG. 9C is a cross section through the combined models232M, 40 as taken along section line 9C-9C in FIG. 9B. FIGS. 10A and 10Bare, respectively, exterior and interior perspective views of theresulting femur jig model 346 after having “saw cut and drill hole data”44 integrated into the jig model 346 to become an integrated or completejig model 348 generally corresponding to the “integrated jig data” 48discussed with respect to [block 150] of FIG. 1E.

As can be understood from FIGS. 3A-3C, the jig blank 50A, which hasselected predetermined dimensions as discussed with respect to FIG. 7,includes an interior surface 230 and an exterior surface 232. Theexterior surface model 232M depicted in FIGS. 8A and 8B is extracted orotherwise created from the exterior surface 232 of the jig blank model50A. Thus, the exterior surface model 232M is based on the jig blankaspect ratio of the femur jig blank 50A selected as discussed withrespect to FIG. 7 and is dimensioned specific to the patient's kneefeatures. The femoral jig surface model 232M can be extracted orotherwise generated from the jig blank model 50A of FIGS. 3A-3C byemploying any of the computer surface rendering techniques describedabove.

As can be understood from FIGS. 9A-9C, the exterior surface model 232Mis combined with the femur surface model 40 to respectively form theexterior and interior surfaces of the femur jig model 346. The femursurface model 40 represents the interior or mating surface of the femurjig 2A and corresponds to the femur arthroplasty target area 42. Thus,the model 40 allows the resulting femur jig 2A to be indexed to thearthroplasty target area 42 of the patient's femur 18 such that theresulting femur jig 2A will matingly receive the arthroplasty targetarea 42 during the arthroplasty procedure. The two surface models 232M,40 combine to provide a patient-specific jig model 346 for manufacturingthe femur jig 2A.

As can be understood from FIGS. 9B and 9C, once the models 232M, 40 areproperly aligned, a gap will exist between the two models 232M, 40. Animage sewing method or image sewing tool is applied to the alignedmodels 232M, 40 to join the two surface models together to form the 3Dcomputer generated jig model 346 of FIG. 9B into a single-piece,joined-together, and filled-in jig model 346 similar in appearance tothe integrated jig model 348 depicted in FIGS. 10A and 10B. In oneembodiment, the jig model 346 may generally correspond to thedescription of the “jig data” 46 discussed with respect [block 145] ofFIG. 1E.

As can be understood from FIGS. 9B and 9C, the geometric gaps betweenthe two models 232M, 40, some of which are discussed below with respectto thicknesses P₁, P₂ and P₃, may provide certain space between the twosurface models 232M, 40 for slot width and length and drill bit lengthfor receiving and guiding cutting tools during TKA surgery. Because theresulting femur jig model 348 depicted in FIGS. 10A and 10B may be a 3Dvolumetric model generated from 3D surface models 232M, 40, a space orgap should be established between the 3D surface models 232M, 40. Thisallows the resulting 3D volumetric jig model 348 to be used to generatean actual physical 3D volumetric femur jig 2.

In some embodiments, the image processing procedure may include a modelrepair procedure for repairing the jig model 346 after alignment of thetwo models 232M, 40. For example, various methods of the model repairinginclude, but are not limit to, user-guided repair, crack identificationand filling, and creating manifold connectivity, as described in:Nooruddin et al., Simplification and Repair of Polygonal Models UsingVolumetric Techniques (IEEE Transactions on Visualization and ComputerGraphics, Vol. 9, No. 2, April-June 2003); C. Erikson, Error Correctionof a Large Architectural Model: The Henderson County Courthouse(Technical Report TR95-013, Dept. of Computer Science, Univ. of NorthCarolina at Chapel Hill, 1995); D. Khorramabdi, A Walk through thePlanned CS Building (Technical Report UCB/CSD 91/652, Computer ScienceDept., Univ. of California at Berkeley, 1991); Morvan et al., IVECS: AnInteractive Virtual Environment for the Correction of .STL files (Proc.Conf. Virtual Design, August 1996); Bohn et al., A Topology-BasedApproach for Shell-Closure, Geometric Modeling for Product Realization,(P. R. Wilson et al., pp. 297-319, North-Holland, 1993); Barequet etal., Filling Gaps in the Boundary of a Polyhedron, Computer AidedGeometric Design (vol. 12, no. 2, pp. 207-229, 1995); Barequet et al.,Repairing CAD Models (Proc. IEEE Visualization '97, pp. 363-370, Oct.1997); and Gueziec et al., Converting Sets of Polygons to ManifoldSurfaces by Cutting and Stitching, (Proc. IEEE Visualization 1998, pp.383-390, Oct. 1998). Each of these references is incorporated into thisDetailed Description in their entireties.

As can be understood from FIGS. 10A and 10B, the integrated jig model348 may include several features based on the surgeon's needs. Forexample, the jig model 348 may include a slot feature 30 for receivingand guiding a bone saw and drill holes 32 for receiving and guiding bonedrill bits. As can be understood from FIGS. 9B and 9C, to providesufficient structural integrity to allow the resulting femur jig 2A tonot buckle or deform during the arthroplasty procedure and to adequatelysupport and guide the bone saw and drill bits, the gap 350 between themodels 232M, 40 may have the following offsets P₁, P₂, and P₃.

As can be understood from FIGS. 9B-10B, in one embodiment, thickness P₁extends along the length of the anterior drill holes 32A between themodels 232M, 40 and is for supporting and guiding a bone drill receivedtherein during the arthroplasty procedure. Thickness P₁ may be at leastapproximately four millimeters or at least approximately fivemillimeters thick. The diameter of the anterior drill holes 32A may beconfigured to receive a cutting tool of at least one-third inches.

Thickness P₂ extends along the length of a saw slot 30 between themodels 232M, 40 and is for supporting and guiding a bone saw receivedtherein during the arthroplasty procedure. Thickness P₂ may be at leastapproximately 10 mm or at least 15 mm thick.

Thickness P₃ extends along the length of the posterior drill holes 32Pbetween the models 232M, 40 and is for supporting and guiding a bonedrill received therein during the arthroplasty procedure. Thickness P₃may be at least approximately five millimeters or at least eightmillimeters thick. The diameter of the drill holes 32 may be configuredto receive a cutting tool of at least one-third inches.

In addition to providing sufficiently long surfaces for guiding drillbits or saws received therein, the various thicknesses P₁, P₂, P₂ arestructurally designed to enable the femur jig 2A to bear vigorous femurcutting, drilling and reaming procedures during the TKR surgery.

As indicated in FIGS. 10A and 10B, the integrated jig model 348 mayinclude: feature 400 that matches the patient's distal portion of themedial condyle cartilage; feature 402 that matches the patient's distalportion of the lateral condyle cartilage; projection 404 that can beconfigured as a contact or a hook and may securely engage the resultingjig 2A onto the patient's anterior femoral joint surface during the TKRsurgery; and the flat surface 406 that provides a blanked labeling areafor listing information regarding the patient, surgeon or/and thesurgical procedure. Also, as discussed above, the integrated jig model348 may include the saw cut slot 30 and the drill holes 32. The innerportion or side 100 of the jig model 348 (and the resulting femur jig2A) is the femur surface model 40, which will matingly receive thearthroplasty target area 42 of the patient's femur 18 during thearthroplasty procedure.

As can be understood by referring to [block 105] of FIG. 1B and FIGS.2A-2F, in one embodiment when cumulating the image scans 16 to generatethe one or the other of the models 40, 22, the models 40, 22 arereferenced to point P, which may be a single point or a series ofpoints, etc. to reference and orient the models 40, 22 relative to themodels 22, 28 discussed with respect to FIG. 1C and utilized for POP.Any changes reflected in the models 22, 28 with respect to point P(e.g., point P becoming point P′) on account of the POP is reflected inthe point P associated with the models 40, 22 (see [block 135] of FIG.1D). Thus, as can be understood from [block 140] of FIG. 1D and FIGS.9A-9C, when the jig blank exterior surface model 232M is combined withthe surface model 40 (or a surface model developed from the arthriticmodel 22) to create the jig model 346, the jig model 346 is referencedand oriented relative to point P′ and is generally equivalent to the“jig data” 46 discussed with respect to [block 145] of FIG. 1E.

Because the jig model 346 is properly referenced and oriented relativeto point P′, the “saw cut and drill hole data” 44 discussed with respectto [block 125] of FIG. 1E can be properly integrated into the jig model346 to arrive at the integrated jig model 348 depicted in FIGS. 10A-10B.The integrated jig model 348 includes the saw cuts 30, drill holes 32and the surface model 40. Thus, the integrated jig model 348 isgenerally equivalent to the “integrated jig data” 48 discussed withrespect to [block 150] of FIG. 1E.

As can be understood from FIG. 11, which illustrates a perspective viewof the integrated jig model 348 mating with the “arthritic model” 22,the interior surface 40 of the jig model 348 matingly receives thearthroplasty target area 42 of the femur lower end 204 such that the jigmodel 348 is indexed to mate with the area 42. Because of thereferencing and orientation of the various models relative to the pointsP, P′ throughout the procedure, the saw cut slot 30 and drill holes 32are properly oriented to result in saw cuts and drill holes that allow aresulting femur jig 2A to restore a patient's joint to a pre-degeneratedcondition.

As indicated in FIG. 11, the integrated jig model 348 may include a jigbody 500, a projection 502 on one side, and two projections 504, 506 theother side of jig body 500. The projections 504, 506 match the medialand lateral condyle cartilage. The projections 502, 504, 506 extendintegrally from the two opposite ends of the jig body 500.

As can be understood from [blocks 155-165] of FIG. 1E, the integratedjig 348 or, more specifically, the integrated jig data 48 can be sent tothe CNC machine 10 to machine the femur jig 2A from the selected jigblank 50A. For example, the integrated jig data 48 may be used toproduce a production file that provides automated jig fabricationinstructions to a rapid production machine 10, as described in thevarious Park patent applications referenced above. The rapid productionmachine 10 then fabricates the patient-specific arthroplasty femur jig2A from the femur jig blank 50A according to the instructions.

The resulting femur jig 2A may have the features of the integrated jigmodel 348. Thus, as can be understood from FIG. 11, the resulting femurjig 2A may have the slot 30 and the drilling holes 32 formed on theprojections 502, 504, 506, depending on the needs of the surgeon. Thedrilling holes 32 are configured to prevent the possible IR/ER(internal/external) rotational axis misalignment between the femoralcutting jig 2A and the patient's damaged joint surface during the distalfemur cut portion of the TKR procedure. The slot 30 is configured toaccept a cutting instrument, such as a reciprocating slaw blade fortransversely cutting during the distal femur cut portion of the TKR.

f. Defining a 3D Surface Model of an Arthroplasty Target Area of a TibiaUpper End for Use as a Surface of an Interior Portion of a TibiaArthroplasty Cutting Jig.

For a discussion of a method of generating a 3D model 40 of a targetarea 42 of a damaged upper end 604 of a patient's tibia 20, reference ismade to FIGS. 12A-12C. FIG. 12A is an anterior-posterior (“AP”) imageslice 608 of the damaged upper or knee joint end 604 of the patient'stibia 20, wherein the image slice 608 includes an open-loop contour linesegment 610 corresponding to the target area 42 of the damaged upper end604. FIG. 12B is a plurality of image slices (16-1, 16-1, 16-2, . . .16-n) with their respective open-loop contour line segments (610-1,610-2, . . . 610-n), the open-loop contour line segments 610 beingaccumulated to generate the 3D model 40 of the target area 42. FIG. 12Cis a 3D model 40 of the target area 42 of the damaged upper end 604 asgenerated using the open-loop contour line segments (16-1, 16-2, . . .16-n) depicted in FIG. 12B.

As can be understood from FIGS. 1A, 1B and 12A, the imager 8 is used togenerate a 2D image slice 16 of the damaged upper or knee joint end 604of the patient's tibia 20. As depicted in FIG. 12A, the 2D image 16 maybe an AP view of the tibia 20. Depending on whether the imager 8 is aMRI or CT imager, the image slice 16 will be a MRI or CT slice. Thedamaged upper end 604 includes the tibia plateau 612, an anterior tibiashaft surface 614, and an area of interest or targeted area 42 thatextends along the tibia meniscus starting from a portion of the lateraltibia plateau surface to the anterior tibia surface 614. The targetedarea 42 of the tibia upper end may be the articulating contact surfacesof the tibia upper end that contact corresponding articulating contactsurfaces of the femur lower or knee joint end.

As shown in FIG. 12A, the image slice 16 may depict the cancellous bone616, the cortical bone 618 surrounding the cancellous bone, and thearticular cartilage lining portions of the cortical bone 618. Thecontour line 610 may extend along the targeted area 42 and immediatelyadjacent the cortical bone and cartilage to outline the contour of thetargeted area 42 of the tibia upper end 604. The contour line 610extends along the targeted area 42 starting at point C on the lateral ormedial tibia plateau 612 (depending on whether the slice 16 extendsthrough the lateral or medial portion of the tibia) and ends at point Don the anterior tibia shaft surface 614.

In one embodiment, as indicated in FIG. 12A, the contour line 610extends along the targeted area 42, but not along the rest of thesurface of the tibia upper end 604. As a result, the contour line 610forms an open-loop that, as will be discussed with respect to FIGS. 12Band 12C, can be used to form an open-loop region or 3D computer model40, which is discussed with respect to [block 140] of FIG. 1D andclosely matches the 3D surface of the targeted area 42 of the tibiaupper end. Thus, in one embodiment, the contour line is an open-loop anddoes not outline the entire cortical bone surface of the tibia upper end604. Also, in one embodiment, the open-loop process is used to form fromthe 3D images 16 a 3D surface model 36 that generally takes the place ofthe arthritic model 36 discussed with respect to [blocks 125-140] ofFIG. 1D and which is used to create the surface model 40 used in thecreation of the “jig data” 46 discussed with respect to [blocks 145-150]of FIG. 1E.

In one embodiment and in contrast to the open-loop contour line 610depicted in FIGS. 12A and 12B, the contour line is a closed-loop contourline generally the same as the closed-loop contour line 210′ discussedwith respect to FIGS. 2D-2E, except the closed-loop contour linepertains to a tibia instead of a femur. Like the femur closed-loopcontour line discussed with respect to FIG. 2D, a tibia closed-loopcontour line may outline the entire cortical bone surface of the tibiaupper end and results in a closed-loop area. The tibia closed-loopcontour lines are combined in a manner similar that discussed withrespect to the femur contour lines in FIG. 2E. As a result, the tibiaclosed-loop area may require the analysis of the entire surface regionof the tibia upper end 604 and result in the formation of a 3D model ofthe entire tibia upper end 604 in a manner similar to the femur upperend 204 illustrated in FIG. 2F. Thus, the 3D surface model resultingfrom the tibia closed-loop process ends up having in common much, if notall, the surface of the 3D tibia arthritic model 36. In one embodiment,the tibia closed-loop process may result in a 3D volumetric anatomicaljoint solid model from the 2D images 16 via applying mathematicalalgorithms. U.S. Pat. No. 5,682,886, which was filed Dec. 26, 1995 andis incorporated by reference in its entirety herein, applies a snakealgorithm forming a continuous boundary or closed-loop. After the tibiahas been outlined, a modeling process is used to create the 3D surfacemodel, for example, through a Bezier patches method. Other 3D modelingprocesses, e.g., commercially-available 3D construction software aslisted in other parts of this Detailed Description, are applicable to 3Dsurface model generation for closed-loop, volumetric solid modeling.

In one embodiment, the closed-loop process is used to form from the 3Dimages 16 a 3D volumetric solid model 36 that is essentially the same asthe arthritic model 36 discussed with respect to [blocks 125-140] ofFIG. 1D. The 3D volumetric solid model 36 is used to create the surfacemodel 40 used in the creation of the “jig data” 46 discussed withrespect to [blocks 145-150] of FIG. 1E.

The formation of a 3D volumetric solid model of the entire tibia upperend employs a process that may be much more memory and time intensivethan using an open-loop contour line to create a 3D model of thetargeted area 42 of the tibia upper end. Accordingly, although theclosed-loop methodology may be utilized for the systems and methodsdisclosed herein, for at least some embodiments, the open-loopmethodology may be preferred over the closed-loop methodology.

An example of a closed-loop methodology is disclosed in U.S. patentapplication Ser. No. 11/641,569 to Park, which is entitled “ImprovedTotal Joint Arthroplasty System” and was filed Jan. 19, 2007. Thisapplication is incorporated by reference in its entirety into thisDetailed Description.

As can be understood from FIGS. 12B and 2G, the imager 8 generates aplurality of image slices (16-1, 16-2 . . . 16-n) via repetitive imagingoperations [block 1000]. Each image slice 16 has an open-loop contourline (610-1, 610-2 . . . 610-n) extending along the targeted region 42in a manner as discussed with respect to FIG. 12A [block 1005]. In oneembodiment, each image slice is a two-millimeter 2D image slice 16. Thesystem 100 compiles the plurality of 2D image slices (16-1, 16-2 . . .16-n) and, more specifically, the plurality of open-loop contour lines(610-1, 610-2, . . . 610-n) into the 3D femur surface computer model 40depicted in FIG. 12C [block 1010]. This process regarding the generationof the surface model 40 is also discussed in the overview section withrespect to [blocks 100-105] of FIG. 1B and [blocks 130-140 ] of FIG. 1D.A similar process may be employed with respect to tibia closed-loopcontour lines.

As can be understood from FIG. 12C, the 3D tibia surface computer model40 is a 3D computer representation of the targeted region 42 of thetibia upper end. In one embodiment, the 3D representation of thetargeted region 42 is a 3D representation of the articulated femurcontact surfaces of the tibia proximal end. As the open-loop generated3D model 40 is a surface model of the relevant femur contacting portionsof the tibia upper end, as opposed to a 3D model of the entire surfaceof the tibia upper end as would be a result of a closed-loop contourline, the open-loop generated 3D model 40 is less time and memoryintensive to generate.

In one embodiment, the open-loop generated 3D model 40 is a surfacemodel of the femur facing end face of the tibia upper end, as opposed a3D model of the entire surface of the tibia upper end. The 3D model 40can be used to identify the area of interest or targeted region 42,which, as previously stated, may be the relevant femur contactingportions of the tibia upper end. Again, the open-loop generated 3D model40 is less time and memory intensive to generate as compared to a 3Dmodel of the entire surface of the tibia proximal end, as would begenerated by a closed-loop contour line. Thus, for at least someversions of the embodiments disclosed herein, the open-loop contour linemethodology is preferred over the closed-loop contour line methodology.However, the system 4 and method disclosed herein may employ either theopen-loop or closed-loop methodology and should not be limited to one orthe other.

Regardless of whether the 3D model 40 is a surface model of the targetedregion 42 (i.e., a 3D surface model generated from an open-loop processand acting as the arthritic model 22) or the entire femur facing endface of the tibia upper end (i.e., a 3D volumetric solid model generatedfrom a closed-loop process and acting as the arthritic model 22), thedata pertaining to the contour lines 610 can be converted into the 3Dcontour computer model 40 via the surface rendering techniques disclosedin any of the aforementioned U.S. patent applications to Park. Forexample, surface rending techniques employed include point-to-pointmapping, surface normal vector mapping, local surface mapping, andglobal surface mapping techniques. Depending on the situation, one or acombination of mapping techniques can be employed.

In one embodiment, the generation of the 3D model 40 depicted in FIG.12C may be formed by using the image slices 16 to determine locationcoordinate values of each of a sequence of spaced apart surface pointsin the open-loop region of FIG. 12B. A mathematical model may then beused to estimate or compute the 3D model 40 in FIG. 12C. Examples ofother medical imaging computer programs that may be used include, butare not limited to: Analyze from AnalyzeDirect, Inc. of Overland Park,Kans.; open-source software such as Paraview of Kitware, Inc.; InsightToolkit (“ITK”) available at www.itk.org; 3D Slicer available atwww.slicer.org; and Mimics from Materialise of Ann Arbor, Mich.

Alternatively or additionally to the aforementioned systems forgenerating the 3D model 40 depicted in FIG. 12C, other systems forgenerating the 3D model 40 of FIG. 12C include the surface renderingtechniques of the Non-Uniform Rational B-spline (“NURB”) program or theBézier program. Each of these programs may be employed to generate the3D contour model 40 from the plurality of contour lines 610.

In one embodiment, the NURB surface modeling technique is applied to theplurality of image slices 16 and, more specifically, the plurality ofopen-loop contour lines 610 of FIG. 2B. The NURB software generates a 3Dmodel 40 as depicted in FIG. 12C, wherein the 3D model 40 has areas ofinterest or targeted regions 42 that contain both a mesh and its controlpoints. For example, see Ervin et al., Landscape Modeling, McGraw-Hill,2001, which is hereby incorporated by reference in its entirety intothis Detailed Description.

In one embodiment, the NURB surface modeling technique employs thefollowing surface equation:

${{G\left( {s,t} \right)} = \frac{\sum\limits_{i = 0}^{k\; 1}\;{\sum\limits_{j = 0}^{k\; 2}\;{{W\left( {i,j} \right)}{P\left( {i,j} \right)}{b_{i}(s)}{b_{j}(t)}}}}{\sum\limits_{i = 0}^{k\; 1}\;{\sum\limits_{j = 0}^{k\; 2}\;{{W\left( {i,j} \right)}{b_{i}(s)}{b_{j}(t)}}}}},$wherein P(i,j) represents a matrix of vertices with nrows=(k1+1) andncols=(k2+1), W(i,j) represents a matrix of vertex weights of one pervertex point, b_(i)(s) represents a row-direction basis or blending ofpolynomial functions of degree M1, b_(j)(t) represents acolumn-direction basis or blending polynomial functions of degree M2, srepresents a parameter array of row-direction knots, and t represents aparameter array of column-direction knots.

In one embodiment, the Bézier surface modeling technique employs theBézier equation (1972, by Pierre Bézier) to generate a 3D model 40 asdepicted in FIG. 12C, wherein the model 40 has areas of interest ortargeted regions 42. A given Bézier surface of order (n, m) is definedby a set of (n+1)(m+1) control points k_(i,j). It maps the unit squareinto a smooth-continuous surface embedded within a space of the samedimensionality as (k_(i,j)). For example, if k are all points in afour-dimensional space, then the surface will be within afour-dimensional space. This relationship holds true for aone-dimensional space, a two-dimensional space, a fifty-dimensionalspace, etc.

A two-dimensional Bézier surface can be defined as a parametric surfacewhere the position of a point p as a function of the parametriccoordinates u, v is given by:

${p\left( {u,v} \right)} = {\sum\limits_{i = 0}^{n}\;{\sum\limits_{j = 0}^{m}\;{{B_{i}^{n}(u)}{B_{j}^{m}(v)}k_{i,j}}}}$evaluated over the unit square, where

${B_{i}^{n}(u)} = {\begin{pmatrix}n \\i\end{pmatrix}{u^{i}\left( {1 - u} \right)}^{n - i}}$is a Bernstein polynomial and

$\begin{pmatrix}n \\i\end{pmatrix} = \frac{n!}{{i!}*{\left( {n - i} \right)!}}$is the binomial coefficient. See Grune et al, On Numerical Algorithm andInteractive Visualization for Optimal Control Problems, Journal ofComputation and Visualization in Science, Vol. 1, No. 4, July 1999,which is hereby incorporated by reference in its entirety into thisDetailed Description.

Various other surface rendering techniques are disclosed in otherreferences. For example, see the surface rendering techniques disclosedin the following publications: Lorensen et al., Marching Cubes: A highResolution 3d Surface Construction Algorithm, Computer Graphics, 21-3:163-169, 1987; Farin et al., NURB Curves & Surfaces: From ProjectiveGeometry to Practical Use, Wellesley, 1995; Kumar et al, RobustIncremental Polygon Triangulation for Surface Rendering, WSCG, 2000;Fleischer et al., Accurate Polygon Scan Conversion Using Half-OpenIntervals, Graphics Gems III, p. 362-365, code: p. 599-605, 1992; Foleyet al., Computer Graphics: Principles and Practice, Addison Wesley,1990; Glassner, Principles of Digital Image Synthesis, Morgan Kaufmann,1995, all of which are hereby incorporated by reference in theirentireties into this Detailed Description.

g. Selecting a Jig Blank Most Similar in Size and/or Configuration tothe Size of the Patient's Tibia Upper End.

As mentioned above, an arthroplasty jig 2, such as a tibia jig 2Bincludes an interior portion 104 and an exterior portion 106. The tibiajig 2B is formed from a tibia jig blank 50B, which, in one embodiment,is selected from a finite number of femur jig blank sizes. The selectionof the tibia jig blank 50B is based on a comparison of the dimensions ofthe patient's tibia upper end 604 to the dimensions and/orconfigurations of the various sizes of tibia jig blanks 50B to selectthe tibia jig blank 50B most closely resembling the patient's tibiaupper end 604 with respect to size and/or configuration. This selectedtibia jig blank 50B has an outer or exterior side or surface 632 thatforms the exterior portion 632 of the tibia jig 2B. The 3D surfacecomputer model 40 discussed with respect to the immediately precedingsection of this Detail Description is used to define a 3D surface 40into the interior side 630 of the computer model of a tibia jig blank50B.

By selecting a tibia jig blank 50B with an exterior portion 632 close insize to the patient's upper tibia end 604, the potential for an accuratefit between the interior portion 630 and the patient's tibia isincreased. Also, the amount of material that needs to be machined orotherwise removed from the jig blank 50B is reduced, thereby reducingmaterial waste and manufacturing time.

For a discussion of a method of selecting a jig blank 50 most closelycorresponding to the size and/or configuration of the patient's uppertibia end, reference is first made to FIGS. 13A-14B. FIG. 13A is a topperspective view of a right tibia cutting jig blank 50BR havingpredetermined dimensions. FIG. 13B is a bottom perspective view of thejig blank 50BR depicted in FIG. 13A. FIG. 13C is plan view of anexterior side or portion 232 of the jig blank 50BR depicted in FIG. 13A.FIG. 14A is a plurality of available sizes of right tibia jig blanks50BR, each depicted in the same view as shown in FIG. 13C. FIG. 14B is aplurality of available sizes of left tibia jig blanks, each depicted inthe same view as shown in FIG. 13C.

A common jig blank 50, such as the right jig blank 50BR depicted inFIGS. 13A-13C and intended for creation of a right tibia jig that can beused with a patient's right tibia, may include a medial tibia footprojection 648 for mating with the medial tibia plateau, a lateral tibiafoot projection 650 for mating with the lateral tibia plateau, aposterior edge 640, an anterior edge 642, a lateral edge 644, a medialedge 646, the exterior side 632 and the interior side 630. The jig blank50BR of FIGS. 13A-13C may be any one of a number of right tibia jigblanks 50BR available in a limited number of standard sizes. Forexample, the jig blank 50BR of FIGS. 13A-13C may be an i-th right tibiajig blank, where i=1, 2, 3, 4, . . . m and m represents the maximumnumber of right tibia jig blank sizes.

As indicated in FIG. 13C, the anterior-posterior extent TAi of the jigblank 50BR is measured from the anterior edge 642 to the posterior edge640 of the jig blank 50BR. The medial-lateral extent TMi of the jigblank 50BR is measured from the lateral edge 644 to the medial edge 646of the jig blank 50BR.

As can be understood from FIG. 14A, a limited number of right tibia jigblank sizes may be available for selection as the right tibia jig blanksize to be machined into the right tibia cutting jig 2B. For example, inone embodiment, there are three sizes (m=3) of right tibia jig blanks50BR available. As can be understood from FIG. 13C, each tibia jig blank50BR has an anterior-posterior/medial-lateral aspect ratio defined asTAi to TMi (e.g., “TAi/TMi” aspect ratio). Thus, as can be understoodfrom FIG. 14A, jig blank 50BR-1 has an aspect ratio defined as“TA₁/TM₁”, jig blank 50BR-2 has an aspect ratio defined as “TA₂/TM₂”,and jig blank 50BR-3 has an aspect ratio defined as “TA₃/TM₃”.

The jig blank aspect ratio is utilized to design right tibia jigs 2Bdimensioned specific to the patient's right tibia features. In oneembodiment, the jig blank aspect ratio can be the exterior dimensions ofthe right tibia jig 2B. In another embodiment, the jig blank aspectratio can apply to the right tibia jig fabrication procedure forselecting the right jig blank 50BR having parameters close to thedimensions of the desired right tibia jig 2B. This embodiment canimprove the cost efficiency of the right tibia jig fabrication processbecause it reduces the amount of machining required to create thedesired jig 2 from the selected jig blank 50.

In FIG. 14A there is a single jig blank aspect ratio depicted for thecandidate tibia jig blank sizes. In embodiments having a greater numberof jig blank aspect ratios for the candidate tibia jig blank sizes, FIG.14A would be similar to FIG. 4A and would have an N-1 direction, andpotentially N-2 and N-3 directions, representing increasing jig blankaspect ratios. The relationships between the various tibia jig blankaspect ratios would be similar to those discussed with respect to FIG.4A for the femur jig blank aspect ratios.

As can be understood from the plot 900 depicted in FIG. 17 and discussedlater in this Detailed Discussion, the E-1 direction corresponds to thesloped line joining Group 1, Group 2 and Group 3 in the plot 900.

As indicated in FIG. 14A, along direction E-1, the jig blank aspectratios remain the same among jigs blanks 50BR-1, 50BR-2 and 50BR-3,where “TA₁/TM₁”=“TA₂/TM₂”=“TA₃/TM₃”. However, comparing to jig blank50BR-1, jig blank 50BR-2 is dimensioned larger and longer than jig blank50BR-1. This is because the TA₂ value for jig blank 50BR-2 increasesproportionally with the increment of its TM₂ value in certain degrees inall X, Y, and Z-axis directions. In a similar fashion, jig blank 50BR-3is dimensioned larger and longer than jig blank 50BR-2 because the TA₃increases proportionally with the increment of its TM₃ value in certaindegrees in all X, Y, and Z-axis directions. One example of the incrementcan be an increase from 5% to 20%. In embodiments where there areadditional aspect ratios available for the tibia jig blank sizes, as wasillustrated in FIG. 4A with respect to the femur jig blank sizes, therelationship between tibia jig blank sizes may be similar to thatdiscussed with respect to FIGS. 4A and 14A.

As can be understood from FIG. 14B, a limited number of left tibia jigblank sizes may be available for selection as the left tibia jig blanksize to be machined into the left tibia cutting jig 2B. For example, inone embodiment, there are three sizes (m=3) of left tibia jig blanks50BL available. As can be understood from FIG. 13C, each tibia jig blank50BL has an anterior-posterior/medial-lateral aspect ratio defined asTAi to TMi (e.g., “TAi/TMi” aspect ratio). Thus, as can be understoodfrom FIG. 14B, jig blank 50BL-1 has an aspect ratio defined as“TA₁/TM₁”, jig blank 50BL-2 has an aspect ratio defined as “TA₂/TM₂”,and jig blank 50BL-3 has an aspect ratio defined as “TA₃/TM₃”.

The jig blank aspect ratio is utilized to design left tibia jigs 2Bdimensioned specific to the patient's left tibia features. In oneembodiment, the jig blank aspect ratio can be the exterior dimensions ofthe left tibia jig 2B. In another embodiment, the jig blank aspect ratiocan apply to the left tibia jig fabrication procedure for selecting theleft jig blank 50BL having parameters close to the dimensions of thedesired left tibia jig 2B. This embodiment can improve the costefficiency of the left tibia jig fabrication process because it reducesthe amount of machining required to create the desired jig 2 from theselected jig blank 50.

In FIG. 14B there is a single jig blank aspect ratio depicted for thecandidate tibia jig blank sizes. In embodiments having a greater numberof jig blank aspect ratios for the candidate tibia jig blank sizes, FIG.14B would be similar to FIG. 4B and would have an N-1 direction, andpotentially N-2 and N-3 directions, representing increasing jig blankaspect ratios. The relationships between the various tibia jig blankaspect ratios would be similar to those discussed with respect to FIG.4B for the femur jig blank aspect ratios.

As indicated in FIG. 14B, along direction E-1, the jig blank aspectratios remain the same among jigs blanks 50BL-1, 50BL-2 and 50BL-3,where “TA₁/TM₁”=“TA₂/TM₂”=“TA₃/TM₃”. However, comparing to jig blank50BL-1, jig blank 50BL-2 is dimensioned larger and longer than jig blank50BL-1. This is because the TA₂ value for jig blank 50BL-2 increasesproportionally with the increment of its TM₂ value in certain degrees inall X, Y, and Z-axis directions. In a similar fashion, jig blank 50BL-3is dimensioned larger and longer than jig blank 50BL-2 because the TA₃increases proportionally with the increment of its TM₃ value in certaindegrees in all X, Y, and Z-axis directions. One example of the incrementcan be an increase from 5% to 20%. In embodiments where there areadditional aspect ratios available for the tibia jig blank sizes, as wasillustrated in FIG. 4B with respect to the femur jig blank sizes, therelationship between tibia jig blank sizes may be similar to thatdiscussed with respect to FIGS. 4B and 14B.

The dimensions of the upper or knee joint forming end 604 of thepatient's tibia 20 can be determined by analyzing the 3D surface model40 or 3D arthritic model 36 in a manner similar to those discussed withrespect to the jig blanks 50. For example, as depicted in FIG. 15, whichis an axial view of the 3D surface model 40 or arthritic model 36 of thepatient's right tibia 20 as viewed in a direction extending proximal todistal, the upper end 604 of the surface model 40 or arthritic model 36may include an anterior edge 660, a posterior edge 662, a medial edge664 and a lateral edge 666. The tibia dimensions may be determined forthe top end face or femur articulating surface 604 of the patient'stibia 20 via analyzing the 3D surface model 40 of the 3D arthritic model36. These tibia dimensions can then be utilized to configure tibia jigdimensions and select an appropriate tibia jig.

As shown in FIG. 15, the anterior-posterior extent tAP of the upper end604 of the patient's tibia 20 (i.e., the upper end 604 of the surfacemodel 40 of the arthritic model 36, whether formed via open orclosed-loop analysis) is the length measured from the anterior edge 660of the tibia plateau to the posterior edge 662 of the tibia plateau. Themedial-lateral extent tML of the upper end 604 of the patient's tibia 20is the length measured from the medial edge 664 of the medial tibiaplateau to the lateral edge 666 of the lateral tibia plateau.

In one embodiment, the anterior-posterior extent tAP and medial-lateralextent tML of the tibia upper end 604 can be used for an aspect ratiotAP/tML of the tibia upper end. The aspect ratios tAP/tML of a largenumber (e.g., hundreds, thousands, tens of thousands, etc.) of patientknees can be compiled and statistically analyzed to determine the mostcommon aspect ratios for jig blanks that would accommodate the greatestnumber of patient knees. This information may then be used to determinewhich one, two, three, etc. aspect ratios would be most likely toaccommodate the greatest number of patient knees.

The system 4 analyzes the upper ends 604 of the patient's tibia 20 asprovided via the surface model 40 of the arthritic model 36 (whether thearthritic model 36 is an 3D surface model generated via an open-loop ora 3D volumetric solid model generated via a closed-loop process), toobtain data regarding anterior-posterior extent tAP and medial-lateralextent tML of the tibia upper ends 604. As can be understood from FIG.16, which depicts the selected model jig blank 50BR of FIG. 13Csuperimposed on the model tibia upper end 604 of FIG. 15, the tibiadimensional extents tAP, tML are compared to the jig blank dimensionalextents TA, TM to determine which jig blank model to select as thestarting point for the machining process and the exterior surface modelfor the jig model.

As shown in FIG. 16, a prospective right tibia jig blank 50BR issuperimposed to mate with the right tibia upper end 604 of the patient'sanatomical model as represented by the surface model 40 or arthriticmodel 36. In one embodiment, the jig blank 50BR may cover the anteriorapproximately two thirds of the tibia plateau, leaving the posteriorapproximately one third of the tibia exposed. Included in the exposedportion of the tibia plateau are lateral and medial exposed regions ofthe tibia plateau, as respectively represented by regions q1 and q2 inFIG. 16. Specifically, exposed region q1 is the region of the exposedtibia plateau between the tibia and jig blank lateral edges 666, 644,and exposed region g2 is the region of the exposed tibia plateau betweenthe tibia and jig blank medial edges 664, 646.

By obtaining and employing the tibia anterior-posterior tAP data and thetibia medial-lateral tML data, the system 4 can size the tibia jig blank50BR according to the following formula: jTML=tML−q1−q2, wherein jTML isthe medial-lateral extent of the tibia jig blank 50BR. In oneembodiment, q1 and q2 will have the following ranges: 2 mm≦q1≦4 mm; and2 mm<q2≦4 mm. In another embodiment, q1 will be approximately 3 mm andq2 will approximately 3 mm.

FIG. 17A is an example scatter plot 900 for selecting from a pluralityof candidate jig blanks sizes a jig blank size appropriate for the upperend 604 of the patient's tibia 20. In one embodiment, the X-axisrepresents the patient's tibia medial-lateral length tML in millimeters,and the Y-axis represents the patient's tibia anterior-posterior lengthtAP in millimeters. In one embodiment, the plot 900 is divided into anumber of jig blank size groups, where each group encompasses a regionof the plot 900 and is associated with a specific parameter TM_(r) of aspecific candidate jig blank size.

In one embodiment, the example scatter plot 900 depicted in FIG. 17A hasthree jig blank size groups, each group pertaining to a single candidatejig blank size. However, depending on the embodiment, a scatter plot 900may have a greater or lesser number of jig blank size groups. The higherthe number of jig blank size groups, the higher the number of thecandidate jig blank sizes and the more dimension specific a selectedcandidate jig blank size will be to the patient's knee features and theresulting jig 2. The more dimension specific the selected candidate jigblank size, the lower the amount of machining required to produce thedesired jig 2 from the selected jig blank 50.

Conversely, the lower the number of jig blank size groups, the lower thenumber of candidate jig blank sizes and the less dimension specific aselected candidate jig blank size will be to the patient's knee featuresand the resulting jig 2. The less dimension specific the selectedcandidate jig blank size, the higher the amount of machining required toproduce the desired jig 2 from the selected jig blank 50, adding extraroughing during the jig fabrication procedure.

The tibia anterior-posterior length tAP may be relevant because it mayserve as a value for determining the aspect ratio TA_(i)/TM_(i). fortibia jig blanks 50B such as those discussed with respect to FIGS.13C-14B and 17A. Despite this, in some embodiments, tibiaanterior-posterior length TA_(i) of the candidate jig blanks may not bereflected in the plot 900 depicted in FIG. 17A or the relationshipdepicted in FIG. 16 because in a practical setting for some embodiments,tibia jig anterior-posterior length may be less significant than tibiajig medial-lateral length. For example, although a patient's tibiaanterior-posterior distance varies according to their knee features, thelength of the foot projection 800, 802 (see FIG. 20A) of a tibia jig 2Bis simply increased without the need to create a jig blank or jig thatis customized to correspond to the tibia anterior-posterior length TA.In other words, in some embodiments, the only difference inanterior-posterior length between various tibia jigs is the differencein the anterior-posterior length of their respective foot projections800, 802.

In some embodiments, as can be understood from FIGS. 16 and 21, theanterior-posterior length of a tibia jig 2B, with its foot projection800, 802, covers approximately half of the tibia plateau. Due in part tothis “half” distance coverage, which varies from patient-to-patient byonly millimeters to a few centimeter, in one embodiment, theanterior-posterior length of the jig may not be of a significantconcern. However, because the jig may cover a substantial portion of themedial-lateral length of the tibia plateau, the medial-lateral length ofthe jig may be of substantial significance as compared to theanterior-posterior length.

While in some embodiments the anterior-posterior length of a tibia jig2B may not be of substantial significance as compared to themedial-lateral length, in some embodiments the anterior-posterior lengthof the tibia jig is of significance. In such an embodiment, jig sizesmay be indicated in FIG. 17A by their aspect ratios TA_(i)/TM_(i) asopposed to just TM_(i). In other words, the jig sizes may be depicted inFIG. 17A in a manner similar to that depicted in FIG. 7A. Furthermore,in such embodiments, FIGS. 14A and 14B may have additional jig blankratios similar to that depicted in FIGS. 4A and 4B. As a result, theplot 900 of 17A may have additional diagonal lines joining the jig blanksizes belonging to each jig blank ratio in a manner similar to thatdepicted in plot 300 of FIG. 7A. Also, in FIG. 17A and in a mannersimilar to that shown in FIG. 7A, there may be additional horizontallines dividing plot 900 according to anterior-posterior length torepresent the boundaries of the various jig blank sizes.

As can be understood from FIG. 17A, in one embodiment, the three jigblank size groups of the plot 900 have parameters TM_(r), TA_(r) asfollows. Group 1 has parameters TM₁, TA1. TM₁ represents themedial-lateral extent of the first tibia jig blank size, wherein TM₁=70mm. TA₁ represents the anterior-posterior extent of the first femoraljig blank size, wherein TA₁=62 mm. Group 1 covers the patient's tibiatML and tAP data wherein 55 mm<tML<70 mm and 45 mm<tAP<75 mm.

Group 2 has parameters TM₂, TA2. TM₂ represents the medial-lateralextent of the second tibia jig blank size, wherein TM₂=85 mm. TA₂represents the anterior-posterior extent of the second femoral jig blanksize, wherein TA₂=65 mm. Group 2 covers the patient's tibia tML and tAPdata wherein 70 mm<tML<85 mm and 45 mm<tAP<75 mm.

Group 3 has parameters TM₃, TA3. TM₃ represents the medial-lateralextent of the third tibia jig blank size, wherein TM₃=100 mm. TA₃represents the anterior-posterior extent of the second femoral jig blanksize, wherein TA₃=68.5 mm. Group 3 covers the patient's tibia tML andtAP data wherein 85 mm<tML<100 mm and 45 mm<tAP<75 mm.

In some embodiments and in contrast to the selection process for thefemur jig blanks discussed with respect to FIGS. 3A-7B, the tibia jigblank selection process discussed with respect to FIGS. 13A-17B may onlyconsider or employ the medial-lateral tibia jig value jTML and relatedmedial-lateral values TM, tML. Accordingly, in such embodiments, theanterior-posterior tibia jig value JTAP and related anterior-posteriorvalues TA, tAP for the tibia jig and tibia plateau are not considered.

As can be understood from FIG. 17B, which is a flow diagram illustratingan embodiment of a process of selecting an appropriately sized jigblank, the bone medial-lateral extent tML is determined for the upperend 604 of the surface model 40 of the arthritic model 36 [block 3000].The medial-lateral bone extent tML of the upper end 604 ismathematically modified according to the above discussed jTML formula toarrive at the minimum tibia jig blank medial-lateral extent jTML [block3010]. The mathematically modified bone medial-lateral extent tML or,more specifically, the minimum tibia jig blank medial-lateral extentjTML is referenced against the jig blank dimensions in the plot 900 ofFIG. 17A [block 3020]. The plot 900 may graphically represent theextents of candidate tibia jig blanks forming a jig blank library. Thetibia jig blank 50B is selected to be the jig blank size having thesmallest extents that are still sufficiently large to accommodate theminimum tibia jig blank medial-lateral extent jTML [block 3030].

In one embodiment, the exterior of the selected jig blank size is usedfor the exterior surface model of the jig model, as discussed below. Inone embodiment, the selected jig blank size corresponds to an actual jigblank that is placed in the CNC machine and milled down to the minimumtibia jig blank anterior-posterior and medial-lateral extents jTAP, jTMLto machine or otherwise form the exterior surface of the tibia jig 2B

The method outlined in FIG. 17B and in reference to the plot 900 of FIG.17A can be further understood from the following example. As measured inFIG. 16 with respect to the upper end 604 of the patient's tibia 20, theextents of the patient's tibia are as follows: tML=85.2 mm [block 3000].As previously mentioned, the upper end 604 may be part of the surfacemodel 40 of the arthritic model 36. Once the tML measurement isdetermined from the upper end 604, the corresponding jig jTML data canbe determined via the above-described jTML formula: jTML=tML−q1−q2,wherein q1=3 mm and q2=3 mm [block 3010]. The result of the jTML formulais jTML=79.2 mm.

As can be understood from the plot 900 of FIG. 17A, the determined jigdata (i.e., jTML=79.2 mm) falls in Group 2 of the plot 900. Group 2 hasthe predetermined tibia jig blank parameters (TM₂) of TM₂=85 mm. Thispredetermined tibia jig blank parameter is the smallest of the variousgroups that are still sufficiently large to meet the minimum tibia blankextents jTML [block 3020]. This predetermined tibia jig blank parameters(TM₂=85 mm) may be selected as the appropriate tibia jig blank size[block 3030].

In one embodiment, the predetermined tibia jig blank parameter (85 mm)can apply to the tibia exterior jig dimensions as shown in FIG. 13C. Inother words, the jig blank exterior is used for the jig model exterioras discussed with respect to FIGS. 18A-19C. Thus, the exterior of thetibia jig blank 50B undergoes no machining, and the unmodified exteriorof the jig blank 50B with its predetermined jig blank parameter (85 mm)serves as the exterior of the finished tibia jig 2B.

In another embodiment, the tibia jig blank parameter (85 mm) can beselected for jig fabrication in the machining process. Thus, a tibia jigblank 50B having a predetermined parameter (85 mm) is provided to themachining process such that the exterior of the tibia jig blank 50B willbe machined from its predetermined parameter (85 mm) down to the desiredtibia jig parameter (79.2 mm) to create the finished exterior of thetibia jig 2B. As the predetermined parameter (85 mm) is selected to berelatively close to the desired femur jig parameter (79.2 mm), machiningtime and material waste are reduced.

While it may be advantageous to employ the above-described jig blankselection method to minimize material waste and machining time, in someembodiments, a jig blank will simply be provided that is sufficientlylarge to be applicable to all patient bone extents tML. Such a jig blankis then machined down to the desired jig blank extent jTML, which serveas the exterior surface of the finished jig 2B.

In one embodiment, the number of candidate jig blank size groupsrepresented in the plot 900 is a function of the number of jig blanksizes offered by a jig blank manufacturer. For example, a first plot 900may pertain only to jig blanks manufactured by company A, which offersthree jig blank sizes. Accordingly, the plot 900 has three jig blanksize groups. A second plot 900 may pertain only to jig blanksmanufactured by company B, which offers six jig blank size groups.Accordingly, the second plot 900 has six jig blank size groups.

A plurality of candidate jig blank sizes exist, for example, in a jigblank library as represented by the plot 900 of FIG. 17B. While eachcandidate jig blank may have a unique combination of anterior-posteriorand medial-lateral dimension sizes, in some embodiments, two or more ofthe candidate jig blanks may share a common aspect ratio tAP/tML orconfiguration. The candidate jig blanks of the library may be groupedalong sloped lines of the plot 900 according to their aspect ratiostAP/tML.

In one embodiment, the jig blank aspect ratio tAP/tML may be used totake a workable jig blank configuration and size it up or down to fitlarger or smaller individuals.

As can be understood from FIG. 17A, a series of 98 OA patients havingknee disorders were entered into the plot 900 as part of a tibia jigdesign study. Each patient's tibia tAP and tML data was measured. Eachpatient tibia tML data was modified via the above-described jTML formulato arrive at the patient's jig blank data (jFML). The patient's jigblank data was then entered into the plot 900 as a point. As can beunderstood from FIG. 17A, no patient point lies outside the parametersof an available group. Such a process can be used to establish groupparameters and the number of needed groups.

In one embodiment, the selected jig blank parameters can be the tibiajig exterior dimensions that are specific to patient's knee features. Inanother embodiment, the selected jig blank parameters can be chosenduring fabrication process.

h. Formation of 3D Tibia Jig Model.

For a discussion of an embodiment of a method of generating a 3D tibiajig model 746 generally corresponding to the “integrated jig data” 48discussed with respect to [block 150] of FIG. 1E, reference is made toFIGS. 13A-13C, FIGS. 18A-18B, FIGS. 19A-19D and FIG. 20A-20B. FIGS.13A-13C are various views of a tibia jig blank 50B. FIGS. 18A-18B are,respectively, exterior and interior perspective views of a tibia jigblank exterior surface model 632M. FIGS. 19A-19D are exteriorperspective views of the tibia jig blank exterior model 632M and bonesurface model 40 being combined. FIGS. 20A and 20B are, respectively,exterior and interior perspective views of the resulting tibia jig model746 after having “saw cut and drill hole data” 44 integrated into thejig model 746 to become an integrated or complete jig model 748generally corresponding to the “integrated jig data” 48 discussed withrespect to [block 150] of FIG. 1E.

As can be understood from FIGS. 13A-13C, the jig blank 50B, which hasselected predetermined dimensions as discussed with respect to FIGS. 17Aand 17B, includes an interior surface 630 and an exterior surface 632.The exterior surface model 632M depicted in FIGS. 18A and 18B isextracted or otherwise created from the exterior surface 632 of the jigblank model 50B. Thus, the exterior surface model 632M is based on thejig blank aspect ratio of the tibia jig blank 50B selected as discussedwith respect to FIGS. 17A and 17B and is dimensioned specific to thepatient's knee features. The tibia jig surface model 632M can beextracted or otherwise generated from the jig blank model 50B of FIGS.13A-13C by employing any of the computer surface rendering techniquesdescribed above.

As can be understood from FIGS. 19A-19C, the exterior surface model 632Mis combined with the tibia surface model 40 to respectively form theexterior and interior surfaces of the tibia jig model 746. The tibiasurface model 40 represents the interior or mating surface of the tibiajig 2B and corresponds to the tibia arthroplasty target area 42. Thus,the model 40 allows the resulting tibia jig 2B to be indexed to thearthroplasty target area 42 of the patient's tibia 20 such that theresulting tibia jig 2B will matingly receive the arthroplasty targetarea 42 during the arthroplasty procedure. The two surface models 632M,40 combine to provide a patient-specific jig model 746 for manufacturingthe tibia jig 2B.

As can be understood from FIGS. 19B and 19C, once the models 632M, 40are properly aligned, a gap will exist between the two models 632M, 40.An image sewing method or image sewing tool is applied to the alignedmodels 632M, 40 to join the two surface models together to form the 3Dcomputer generated jig model 746 of FIG. 19B into a single-piece,joined-together, and filled-in jig model 746 similar in appearance tothe integrated jig model 748 depicted in FIGS. 20A and 20B. In oneembodiment, the jig model 746 may generally correspond to thedescription of the “jig data” 46 discussed with respect [block 145] ofFIG. 1E.

As can be understood from FIGS. 19B-19D, 20A and 20B, the geometric gapsbetween the two models 632M, 40, some of which are discussed below withrespect to thicknesses V₁, V₂ and V₃, may provide certain space betweenthe two surface models 632M, 40 for slot width and length and drill bitlength for receiving and guiding cutting tools during TKA surgery.Because the resulting tibia jig model 748 depicted in FIGS. 20A and 20Bmay be a 3D volumetric model generated from 3D surface models 632M, 40,a space or gap should be established between the 3D surface models 632M,40. This allows the resulting 3D volumetric jig model 748 to be used togenerate an actual physical 3D volumetric tibia jig 2B.

In some embodiments, the image processing procedure may include a modelrepair procedure for repairing the jig model 746 after alignment of thetwo models 632M, 40. For example, various methods of the model repairinginclude, but are not limit to, user-guided repair, crack identificationand filling, and creating manifold connectivity, as described in:Nooruddin et al., Simplification and Repair of Polygonal Models UsingVolumetric Techniques (IEEE Transactions on Visualization and ComputerGraphics, Vol. 9, No. 2, April-June 2003); C. Erikson, Error Correctionof a Large Architectural Model: The Henderson County Courthouse(Technical Report TR95-013, Dept. of Computer Science, Univ. of NorthCarolina at Chapel Hill, 1995); D. Khorramabdi, A Walk through thePlanned CS Building (Technical Report UCB/CSD 91/652, Computer ScienceDept., Univ. of California at Berkeley, 1991); Morvan et al., IVECS: AnInteractive Virtual Environment for the Correction of .STL files (Proc.Conf. Virtual Design, August 1996); Bohn et al., A Topology-BasedApproach for Shell-Closure, Geometric Modeling for Product Realization,(P. R. Wilson et al., pp. 297-319, North-Holland, 1993); Barequet etal., Filling Gaps in the Boundary of a Polyhedron, Computer AidedGeometric Design (vol. 12, no. 2, pp. 207-229, 1995); Barequet et al.,Repairing CAD Models (Proc. IEEE Visualization '97, pp. 363-370, October1997); and Gueziec et al., Converting Sets of Polygons to ManifoldSurfaces by Cutting and Stitching, (Proc. IEEE Visualization 1998, pp.383-390, October 1998). Each of these references is incorporated intothis Detailed Description in their entireties.

As can be understood from FIGS. 20A and 20B, the integrated jig model748 may include several features based on the surgeon's needs. Forexample, the jig model 748 may include a slot feature 30 for receivingand guiding a bone saw and drill holes 32 for receiving and guiding bonedrill bits. As can be understood from FIGS. 19B and 19C, to providesufficient structural integrity to allow the resulting tibia jig 2B tonot buckle or deform during the arthroplasty procedure and to adequatelysupport and guide the bone saw and drill bits, the gap between themodels 232M, 40 may have the following offsets V₁, V₂, and V₃.

As can be understood from FIGS. 19B-20B, in one embodiment, thickness V₁extends along the length of the posterior drill holes 32P between themodels 632M, 40 and is for supporting and guiding a bone drill receivedtherein during the arthroplasty procedure. Thickness V₁ may be at leastapproximately four millimeters or at least approximately fivemillimeters thick. The diameter of the posterior drill holes 32P may beconfigured to receive a cutting tool of at least one-third inches.

Thickness V₂ extends is the thickness of the jig foots 800, 802 betweenthe inner and exterior surfaces 40, 632M. The thickness providesadequate structural strength for jig foots 800, 802, to resist bucklingand deforming of the jig to manufacture and use. Thickness V₂ may be atleast approximately five millimeters or at least eight millimetersthick.

Thickness V₃ extends along the length of a saw slot 30 between themodels 632M, 40 and is for supporting and guiding a bone saw receivedtherein during the arthroplasty procedure. Thickness V₃ may be at leastapproximately 10 mm or at least 15 mm thick.

In addition to providing sufficiently long surfaces for guiding drillbits or saws received therein, the various thicknesses V₁, V₂, V₂ arestructurally designed to enable the tibia jig 2B to bear vigorous tibiacutting, drilling and reaming procedures during the TKR surgery.

As indicated in FIGS. 20A and 20B, the exterior portion or side 106 ofthe integrated jig model 748 may include: jig foot or feature 800 thatextends over and matches the patient's medial portion of the tibiaplateau; jig foot or feature 802 that extends over and matches thepatient's lateral portion of the tibia plateau; projection 804 thatextends downward from the upper exterior surface 632 of the tibia jig2B; and a flat portion of the exterior surface 632 that provides ablanked labeling area for listing information regarding the patient,surgeon or/and the surgical procedure. Also, as discussed above, theintegrated jig model 748 may include the saw cut slot 30 and the drillholes 32. The inner portion or side 104 of the jig model 748 (and theresulting tibia jig 2B) is the tibia surface model 40, which willmatingly receive the arthroplasty target area 42 of the patient's tibia20 during the arthroplasty procedure.

As can be understood by referring to [block 105] of FIG. 1B and FIGS.12A-12C, in one embodiment when cumulating the image scans 16 togenerate the one or the other of the models 40, 22, the models 40, 22are referenced to point P, which may be a single point or a series ofpoints, etc. to reference and orient the models 40, 22 relative to themodels 22, 28 discussed with respect to FIG. 1C and utilized for POP.Any changes reflected in the models 22, 28 with respect to point P(e.g., point P becoming point P′) on account of the POP is reflected inthe point P associated with the models 40, 22 (see [block 135] of FIG.1D). Thus, as can be understood from [block 140] of FIG. 1D and FIGS.19A-19C, when the jig blank exterior surface model 632M is combined withthe surface model 40 (or a surface model developed from the arthriticmodel 22) to create the jig model 746, the jig model 746 is referencedand oriented relative to point P′ and is generally equivalent to the“jig data” 46 discussed with respect to [block 145] of FIG. 1E.

Because the jig model 746 is properly referenced and oriented relativeto point P′, the “saw cut and drill hole data” 44 discussed with respectto [block 125] of FIG. 1E can be properly integrated into the jig model746 to arrive at the integrated jig model 748 depicted in FIGS. 20A-20B.The integrated jig model 748 includes the saw cuts 30, drill holes 32and the surface model 40. Thus, the integrated jig model 748 isgenerally equivalent to the “integrated jig data” 48 discussed withrespect to [block 150] of FIG. 1E.

As can be understood from FIG. 21, which illustrates a perspective viewof the integrated jig model 748 mating with the “arthritic model” 22,the interior surface 40 of the jig model 748 matingly receives thearthroplasty target area 42 of the tibia upper end 604 such that the jigmodel 748 is indexed to mate with the area 42. Because of thereferencing and orientation of the various models relative to the pointsP, P′ throughout the procedure, the saw cut slot 30 and drill holes 32are properly oriented to result in saw cuts and drill holes that allow aresulting tibia jig 2B to restore a patient's joint to a pre-degeneratedcondition.

As indicated in FIG. 21, the integrated jig model 748 may include a jigbody 850, a medial tibia plateau covering projection 852, a lateraltibia plateau covering projection 854, a lower portion 856 extendingform the body 850, posterior drill holes 32P, anterior drill holes 32A,a saw slot 30 and an upper flat portion 856 for receiving thereonpatient, surgery and physician data. The projections 852, 854 extendover their respective medial and lateral tibia plateau portions. Theprojections 852, 854, 856 extend integrally from the jig body 850.

As can be understood from [blocks 155-165] of FIG. 1E, the integratedjig 748 or, more specifically, the integrated jig data 48 can be sent tothe CNC machine 10 to machine the tibia jig 2B from the selected jigblank 50B. For example, the integrated jig data 48 may be used toproduce a production file that provides automated jig fabricationinstructions to a rapid production machine 10, as described in thevarious Park patent applications referenced above. The rapid productionmachine 10 then fabricates the patient-specific arthroplasty tibia jig2B from the tibia jig blank 50B according to the instructions.

The resulting tibia jig 2B may have the features of the integrated jigmodel 748. Thus, as can be understood from FIG. 21, the resulting tibiajig 2B may have the slot 30 and the drilling holes 32 formed on theprojections 852, 854, 856, depending on the needs of the surgeon. Thedrilling holes 32 are configured to prevent the possible IR/ER(internal/external) rotational axis misalignment between the tibiacutting jig 2B and the patient's damaged joint surface during theproximal tibia cut portion of the TKR procedure. The slot 30 isconfigured to accept a cutting instrument, such as a reciprocating slawblade for transversely cutting during the proximal tibia cut portion ofthe TKR.

Although the present invention has been described with reference topreferred embodiments, persons skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

1. A method of manufacturing an arthroplasty jig, the method comprising:generating two-dimensional images of at least a portion of a boneforming a joint; using at least one computer processor to generate afirst three-dimensional computer model of the at least a portion of thebone from the two-dimensional images; using at least one computerprocessor to generate a second three-dimensional computer model of theat least a portion of the bone from the two-dimensional images; causingthe first and second three-dimensional computer models to have in commona reference position, wherein the reference position includes at leastone of a location or an orientation relative to an origin; generating afirst type of data with the first three-dimensional computer model,wherein the first three-dimensional computer model is a bone only model;generating a second type of data with the second three-dimensionalcomputer model, wherein the second three-dimensional computer model is abone and cartilage model; employing the reference position to integratethe first and second types of data into an integrated jig data; andusing the integrated jig data at a manufacturing machine to manufacturethe arthroplasty jig.
 2. The method of claim 1, wherein the bone onlyand bone and cartilage models represent a degenerated state of thejoint.
 3. The method of claim 1, wherein the first type of data includesat least one of saw cut or drill hole information, and the second typeof data includes surface contour information of the at least a portionof the bone.
 4. The method of claim 3, wherein the saw cut and drillhole information includes at least one of location, orientation or sizeof at least one of a proposed arthroplasty saw cut or drill hole.
 5. Themethod of claim 1, wherein the second three-dimensional computer modelis generated at least in part from open-loop contour lines derived atleast in part from the two-dimensional images.
 6. The method of claim 1,wherein the second three-dimensional computer model is generated atleast in part from closed-loop contour lines derived at least in partfrom the two-dimensional images.
 7. The method of claim 1, wherein thefirst three-dimensional computer model is a three-dimensional volumetricmodel.
 8. The method of claim 1, wherein the second three-dimensionalcomputer model is a three-dimensional surface model.
 9. The method ofclaim 1, wherein the two-dimensional images are MRI images.
 10. Themethod of claim 1, wherein the two-dimensional images are CT images. 11.The method of claim 1, wherein the reference position is at least one ofa point, multiple points, a vector, a plane, or a plane plus a point.12. The method of claim 1, wherein the reference position is near thejoint in the two-dimensional images.
 13. The method of claim 1, whereinthe joint is at least one of a knee, elbow, wrist, ankle, shoulder, hipor vertebrae interface.
 14. The method of claim 1, wherein a change inlocation or orientation relative to the origin for one of thethree-dimensional models causes an equal change in location ororientation relative to the origin for the other of thethree-dimensional models.
 15. The method of claim 1, further comprising:comparing dimensions of the at least a portion of the bone to candidatejig blanks; selecting from the candidate jig blanks a jig blank with thesmallest dimensions that are able to accommodate the dimensions of theat least a portion of the bone; and providing the selected jig blank tothe manufacturing machine.
 16. The method of claim 15, furthercomprising: mathematically modifying the dimensions of the at least aportion of the bone and using the mathematically modified dimensions indetermining which candidate jig blank to select.
 17. The method of claim15, where the dimensions of the at least a portion of the bone areobtained from at least one of the two-dimensional images or thethree-dimensional images.
 18. An arthroplasty jig manufactured accordingto claim
 1. 19. A method of manufacturing an arthroplasty jig, themethod comprising: generating two-dimensional images of at least aportion of a bone forming a joint; using at least one computer processorto generate a first three-dimensional computer model of the at least aportion of the bone from the two-dimensional images; using at least onecomputer processor to generate a second three-dimensional computer modelof the at least a portion of the bone from the two-dimensional images;causing the first and second three-dimensional computer models to havein common a reference position, wherein the reference position includesat least one of a location or an orientation relative to an origin;generating a first type of data with the first three-dimensionalcomputer model, wherein the first three-dimensional computer modelrepresents an approximation of the at least a portion of the bone in apre-degenerated state; generating a second type of data with the secondthree-dimensional computer model, wherein the second three-dimensionalcomputer model represents the at least a portion of the bone withcartilage in a degenerated state; employing the reference position tointegrate the first and second types of data into an integrated jigdata; and using the integrated jig data at a manufacturing machine tomanufacture the arthroplasty jig.
 20. A method of manufacturing anarthroplasty jig, the method comprising: generating two-dimensionalimages of at least a portion of a bone forming a joint; extending anopen-loop contour line along an arthroplasty target region in at leastsome of the two-dimensional images; using at least one computerprocessor to generate a three-dimensional computer model of thearthroplasty target region from the open-loop contour lines, wherein thethree-dimensional computer model is a bone and cartilage model;generating from the three-dimensional computer model surface contourdata pertaining to the arthroplasty target area; and using the surfacecontour data at a manufacturing machine to manufacture the arthroplastyjig.
 21. The method of claim 20, wherein the bone and cartilage modelrepresents a degenerated state of the joint.
 22. The method of claim 20,wherein the three-dimensional computer model is a three-dimensionalsurface model.
 23. The method of claim 20, wherein the two-dimensionalimages are MRI images.
 24. The method of claim 20, wherein thetwo-dimensional images are CT images.
 25. The method of claim 20,wherein the joint is at least one of a knee, elbow, wrist, ankle,shoulder, hip or vertebrae interface.
 26. The method of claim 20,further comprising: comparing dimensions of the at least a portion ofthe bone to candidate jig blanks; selecting from the candidate jigblanks a jig blank with the smallest dimensions that are able toaccommodate the dimensions of the at least a portion of the bone; andproviding the selected jig blank to the manufacturing machine.
 27. Themethod of claim 26, further comprising: mathematically modifying thedimensions of the at least a portion of the bone and using themathematically modified dimensions in determining which candidate jigblank to select.
 28. The method of claim 27, where the dimensions of theat least a portion of the bone are obtained from at least one of thetwo-dimensional images or the three-dimensional images.
 29. The methodof claim 20, wherein the open-loop contour lines extend immediatelyadjacent cortical bone and cartilage of the arthroplasty target region.